Clephas

1) Yes, a definite yes.  I love sister routes, especially twin sister routes.  I have a thing for the forbidden and obsessively passionate relationships when it comes to romance, and sister routes tend to provide that more often than the regular 'I just met you but I love you' sort of VN romance.
 
2) I don't believe in censorship in literature or complete fiction, though I personally despise rape and am not fond of hard BDSM (anything beyond a blindfold or maybe tying the hands makes me wither, lol).  My only stipulation is that one should also understand where pro-censorship people are coming from.  In their eyes, fiction is not just fiction, it something a writer could see themselves doing in many cases.  Also, you shouldn't underestimate the amount of influence the written word can have on the reader.  A half a decade ago, I would have considered it disgusting to speak about my personal fetishes with others, and now I have no problem making jokes about it.  That is almost entirely due to my obsessive playing of VNs.  It is this influence that pro-censorship people fear, and it is a legitimate fear... though fear is not a good enough reason to ignore the principles of free speech.  Vulgarity and the like are matters of subjective perspective, and as such they are not legitimate reasons to suppress the freedom of expression. 

Shiranui Yoshikazu of Evolimit (I play this every two years, lol).  A brave pervert incapable of feeling sorrow who pushes on through even the worst of situations.

The key to making a truly good 'bad' ending is including a level of conclusiveness to it in the greater context of events.  Bad endings which are basically random are generally useless (make one bad choice and all of the sudden the MC dies, for instance).  However, if you include at least some progression after the choice or set of choices that creates the route to the bad ending, you can bring it to life in and of itself.  Essentially that is what utsuge do.  The best of them create a conclusive narrative that makes sense within the greater narrative as is defined by the 'true' ending. 
A lot of writers - particularly the ones that use the ladder-style choice structure - botch things here by creating a true route that invalidates all other endings due to setting elements included.  Aiyoku no Eustia  is a classic example of a botched attempt at a true ending, as the true ending completely invalidates the story of the other endings.  
This isn't much of an issue if you read slowly (those who read a single VN over the course of months or a year), but for someone who finishes an average-sized VN within a week or a month, it is a glaring flaw.  Even small inconsistencies and setting clashes standout in that case, and it is glaringly obvious in the case of VNs with true endings or grand routes.  
In Akeiro Kaikitan, while there is a true ending, no single ending is neglected.  All of them are somewhat bittersweet and some are downright bad (Youko's ending comes to mind, as it is the result of literally everything going wrong).  My favorite path in the game, the path for the tochigami twins, is a classic example of how a bittersweet ending can leave an intense impression that overshadows the true ending.  As cathartic endings go, it is pretty close to the ideal.
Another game that can be considered mostly extended bad endings is Jingai Makyou (by Nitroplus).  Even the single 'happiest' ending in the game is an ending where the protagonist casts aside his humanity, for instance.  Even then, it is a matter of interpretation, as some would find the alternate endings for the same path to be 'better' depending on their outlook, even if it cost the characters deeply in the process.  
Yet another approach I experienced in the past is the one used in Ore no Tsure wa Hitodenashi.  In this one, the endings are separated into 'blue' and 'Happy' endings.  The happy endings are just that, straight-out happy endings.  However, the blue endings are endings where the inhuman heroines follow their darker desires and things go in a completely different direction.  This utilizes the drastic contrast to enhance the experience both ways.  It also built up the characterizations in a way that was surprisingly effective.

It's better if I give an example here.  The example I'm offering up is Houkago no Futekikakusha.  Houkago no Futekikakusha is undeniably an incredibly brutal utsuge... but the true ending can be considered a 'good' ending... if you ignore the fact that in all the alternative timelines, those horrible events still happened.  The main difference between a nakige and an utsuge is that nakige always result in a 'good' ending, even if it is a bit bittersweet, whereas an utsuge's endings will mostly be sad or despairing endings (a single ending can be an exception, but anything more than that and it isn't quite an utsuge).  
That should answer most of your questions, but I'll go ahead and put up another example... in this case, a chuunige.  Chuunige generally have bittersweet endings, with truly happy endings being relatively rare.  The one I want to mention is Silverio Trinity (second in the series).  Spoilers below:
Because of this, it fits your condition of a single ending being 'good' while all the others are bitter or sad.  This particular tactic, which is usually used to enhance the emotional response of the reader to the final 'good' ending, can have great results or horrible ones depending on how that last ending is handled.  To be blunt, I've read VNs where a writer took this tactic and ran it into the ground because he couldn't write a sufficiently standout good path to contrast with the bad ones.  The most effective tactic in this case is to path-lock so that one can only reach the good ending by experiencing all or at least one of the bad endings, then making the good ending highly detailed and emotionally impactful (made even moreso by the experience of the other paths).  
 

It's not an unusual concept.  To be blunt, Sunao's ending in Semiramis no Tenbin is basically a bad ending that happens if you miss the flag for Ami's ending.  As for bad endings that are longer than the good endings... less common but also something that happens regularly in utsuge in particular.  Sora no Baroque comes to mind, for instance.
However, you have to ask yourself... do you really want a bad ending to be the one thing people remember when it is all over?  Because the longest and most detailed endings are the ones people remember the most.  In good VNs, the true ending generally is never shorter than the other endings and is often longer many times over for this precise reason.  It is also why - if a heroine exists for the true ending - picking a poor quality heroine for the true ending usually damns the game to the kusoge pile.

It's not an unusual concept.  To be blunt, Sunao's ending in Semiramis no Tenbin is basically a bad ending that happens if you miss the flag for Ami's ending.  As for bad endings that are longer than the good endings... less common but also something that happens regularly in utsuge in particular.  Sora no Baroque comes to mind, for instance.
However, you have to ask yourself... do you really want a bad ending to be the one thing people remember when it is all over?  Because the longest and most detailed endings are the ones people remember the most.  In good VNs, the true ending generally is never shorter than the other endings and is often longer many times over for this precise reason.  It is also why - if a heroine exists for the true ending - picking a poor quality heroine for the true ending usually damns the game to the kusoge pile.

Looks like it might not contain the contents from Superior.  It does contain Mitori and Hishia's routes though.  Superior is a non-heroine path that branches off the events of Saku's path.

It's not an unusual concept.  To be blunt, Sunao's ending in Semiramis no Tenbin is basically a bad ending that happens if you miss the flag for Ami's ending.  As for bad endings that are longer than the good endings... less common but also something that happens regularly in utsuge in particular.  Sora no Baroque comes to mind, for instance.
However, you have to ask yourself... do you really want a bad ending to be the one thing people remember when it is all over?  Because the longest and most detailed endings are the ones people remember the most.  In good VNs, the true ending generally is never shorter than the other endings and is often longer many times over for this precise reason.  It is also why - if a heroine exists for the true ending - picking a poor quality heroine for the true ending usually damns the game to the kusoge pile.

It's not an unusual concept.  To be blunt, Sunao's ending in Semiramis no Tenbin is basically a bad ending that happens if you miss the flag for Ami's ending.  As for bad endings that are longer than the good endings... less common but also something that happens regularly in utsuge in particular.  Sora no Baroque comes to mind, for instance.
However, you have to ask yourself... do you really want a bad ending to be the one thing people remember when it is all over?  Because the longest and most detailed endings are the ones people remember the most.  In good VNs, the true ending generally is never shorter than the other endings and is often longer many times over for this precise reason.  It is also why - if a heroine exists for the true ending - picking a poor quality heroine for the true ending usually damns the game to the kusoge pile.

My top ten VN soundtracks
Evolimit
Komorebi no Nostalgica
Hapymaher
Silverio Series 
Akeiro Kaikitan
Ikusa Megami Zero
Draculius
Kitto, Todoku Sumiwataru Asairo Yori Mo
Yami to Hikari no Sanctuary 
Devils Devel Concept
 

My top ten VN soundtracks
Evolimit
Komorebi no Nostalgica
Hapymaher
Silverio Series 
Akeiro Kaikitan
Ikusa Megami Zero
Draculius
Kitto, Todoku Sumiwataru Asairo Yori Mo
Yami to Hikari no Sanctuary 
Devils Devel Concept
 

Something to keep in mind with replaying a VN is that 'normal' VNs really aren't suitable for being played repeatedly.  In my experience, there are a few golden standards (though not absolute ones) that enhance the replayability of a VN.
1) Depth of the Setting- This is one of the two primary reasons why I'm most likely to replay a VN.  If a setting is deep enough, there is very little chance you will catch everything on a first playthrough, so games with deep settings often take two or three replays to start to feel stale.
2) Emotionality/Catharsis- The degree to which a VN stimulates the emotions through presentation and story can often make a VN that is otherwise not all that special replayable.  For this reason, nakige are some of the most commonly replayed VNs from my conversations over the years with other VN players.  If it makes you cry, it is probably worth trying again, lol.
3) Presentation (dramatic, memorable)- In some cases, there is just something about the way the story is presented that makes replaying a VN easy.  
4) Uniqueness- Though this became rarer and rarer as time went on, this quality is often enough to make me go back to a VN.  Semiramis no Tenbin and Re:Birth Colony both fall into this type, for different reasons.
 

Baldr Bringer.  Baldr Bringer's story is virtually nonexistent, and the combat is awful and slow-paced (the attraction of the Baldr series battle systems' was how fast-paced it was).  
Senkou no Clarias (the last gameplay game by Giga's Team Baldrhead) was interesting... until it wasn't.  The combat system was clunky and poorly designed, though not as poorly as Baldr Bringer's.

I played the Baldr series up to the point where they for some reason decided to make the last game a piece of crap (both battle system and story).  I still don't get why they destroyed the traditions of the series to create a mindless game obviously designed for mobile phones rather than pc or consoles.  
Giga has been showing signs of collapse for a while now.  The over-production of the 'kiss' series, which was never that popular even amongst romance VN lovers, was another sign of this.  In addition, Giga's development costs were always excessive for the genre, which probably made it worse due to the borderline nature of sales of VNs.
Harvest Overray was decent, but after that I came to the conclusion that Giga was incapable of producing anything truly superlative outside of the Baldr series.  This was confirmed by my first attempt to play a game from the 'kiss' series, which was a total kusoge.

I played the Baldr series up to the point where they for some reason decided to make the last game a piece of crap (both battle system and story).  I still don't get why they destroyed the traditions of the series to create a mindless game obviously designed for mobile phones rather than pc or consoles.  
Giga has been showing signs of collapse for a while now.  The over-production of the 'kiss' series, which was never that popular even amongst romance VN lovers, was another sign of this.  In addition, Giga's development costs were always excessive for the genre, which probably made it worse due to the borderline nature of sales of VNs.
Harvest Overray was decent, but after that I came to the conclusion that Giga was incapable of producing anything truly superlative outside of the Baldr series.  This was confirmed by my first attempt to play a game from the 'kiss' series, which was a total kusoge.

Try reading the Ln or the web novel.  So far it is pretty close to the web novel, with the exception of skipping over a lot of the school life shit.  The details that includes will fill in the characters to an extent.  As for Delta and the others, you don't really get to know them until later in the story.  Alpha and Beta are the ones who have the most 'screen time' in the story, with Ipsilon coming to life pretty late in the story.  Delta is really simple (literally simple)... she's basically a wolf to the bone.  If you can beat her up, she's submissive, if you lose to her, she dominates you.  Her main interests are food and killing.

Naturally?  Whenever I needed to cleanse my palate of the taste of kusoge, I went back and played something good.  

Naturally?  Whenever I needed to cleanse my palate of the taste of kusoge, I went back and played something good.  

Evolimit
Tokyo Babel
Dies Irae
Draculius
Amatsutsumi
Mirai Nostalgia
Aoi Tori
Devils Devel Concept
Soshite Hatsukoi wa Imouto ni Naru
Minamijuujisei Renka
Paradise Lost
Kajiri Kamui Kagura
Yurikago yori Tenshi Made
Haru to Yuki
Eden*
Eien no Aselia
Silverio Vendetta
Silverio Trinity
Zero Infinity
Vermilion Bind of Blood
Electro-Arms
Muramasa
Akatsuki no Goei trilogy
Karenai Sekai to Owaru Hana
Akeiro Kaikitan
Nanairo Reincarnation
Ikusa Megami Zero
Bradyon Veda
Bullet Butlers
Kikan Bakumatsu Ibun Last Cavalier
Ayakashibito
Chrono Belt
Cross Channel
Tsukihime
FSN
Comyu
Rui wa Tomo o Yobu and fandisc
Hapymaher
Haruka ni Aogi, Uruwashi no
Lovekami (original)
Jingai Makyou
Koisuru Otome to Shugo no Tate (both)
Komorebi no Nostalgica
Tiny Dungeon series
Valkyrie Runabout
Majikoi
Ou no Mimi ni wa Todokanai
Phantom of Inferno
Otome ga Tsumugu Koi no Canvas
Ryuukishi Bloody Saga
Suzunone Seven
Kamikaze Explorer
Tenshi no Hane o Fumanaide
Tsuisou no Augment (both)
Yomegami
Yami to Hikari no Sanctuary
Suisei Ginka
Hello, Lady (all versions)
Konata yori Kanata made
Houkago no Futekigousha
Semiramis no Tenbin
Baldr Skydive
Baldr Sky Zero
Ojousama no Hanbun wa Ren'ai de Dekiteimasu
Ojousama wa Gokigen Naname
Dracu-Riot
Kin'iro Loveriche (and fandisc)
Campus's Uso series
Bloody Rondo
Gensou no Idea
Shinigami no Testament
Natsuiro Recipe
Venus Blood Hypno (known as Hollow in the West)
Shuumatsu Shoujo Gensou Alicematic
Tayutama (original)
World Election
Prism Recollection
Haruru Minamo ni
Duelist x Engage
ExE
PrimalXHearts
Sakura, Sakimashita
Abyss Homicide Club
Amairo Islenauts
Blade x Bullet
Shirogane no Soleil
Fake Azure Arcology
Re:Birth Colony Lost Azurite
Hyakka Ryouran Elixir
Kanojo-Tachi no Ryuugi
Kono Sekai no Mukou de
Kouyoku no Soleil
Primary
Lunaris Filia
HHG
Sakura Iro Quartet
Otomimi Infinity
Reminiscence (for Aki's route)
Toppara
 

Keep in mind that Kamishino had over a decade to get translated, and yet it was only finished recently as a passion project.  Moreover, though the initial translation was done some time ago, it was only recently that it was actually released.  I imagine if a potential translator plays the translated version and wants the two remaining paths, it might be a possibility.  However, keep in mind that most fan-translations fall apart for a reason, and those two paths are a prime candidate for manufacturing such a reason (they are unnecessarily long for the actual content contained within the path, as well as having a more H focus than the other four paths).

Keep in mind that Kamishino had over a decade to get translated, and yet it was only finished recently as a passion project.  Moreover, though the initial translation was done some time ago, it was only recently that it was actually released.  I imagine if a potential translator plays the translated version and wants the two remaining paths, it might be a possibility.  However, keep in mind that most fan-translations fall apart for a reason, and those two paths are a prime candidate for manufacturing such a reason (they are unnecessarily long for the actual content contained within the path, as well as having a more H focus than the other four paths).

Keep in mind that Kamishino had over a decade to get translated, and yet it was only finished recently as a passion project.  Moreover, though the initial translation was done some time ago, it was only recently that it was actually released.  I imagine if a potential translator plays the translated version and wants the two remaining paths, it might be a possibility.  However, keep in mind that most fan-translations fall apart for a reason, and those two paths are a prime candidate for manufacturing such a reason (they are unnecessarily long for the actual content contained within the path, as well as having a more H focus than the other four paths).

As an answer to the question above, I'm not interested in tlcing the remaining two paths.   I more or less agree with Ittaku about those two paths, from personal experience.  In addition, those two paths are ridiculously long despite the lack of any real content to them, so in this case it really isn't worth the effort.  
It is painful to read those paths, it would be even more painful to have to help translate them.

Madohi Shiroki Kamikakushi (Edit: Osananajimi end is the true end)
Kurogane Kaikitan 
Waga Himegimi ni Eikan (Majinzoku side end is the true end, all three national paths are satisfying, side-heroines get gypped)
Edit: Oh I forgot.
Kunado Kokuki

Irotoridori is the only surprise on that list... I'd more or less given up on seeing anymore Favorite games being translated.
Hopefully, Sakura Moyu will come eventually (Favorite's best work).