Thinks your good idea. I finally can use a uncen game's cg to replace the origin game. Just extract the uncen game's cg file(e.g: cg.ypf) and the origin game's. Replace the origin game's cg and then repack as 'update1.ypf'(I use ypf manager tool).Finally, delete 'cg.ypf'.
it don't need the pack key, and it work well.