Indeed, KH2 story was the best in the series so far. Xenahort's story, the Organization, Ansem and the nobodies was really much better than the shadows story in KH1. Plus it gave much more room for expansion ;)
Also, i'm thinking Ven is to Roxas what Roxas is to Sora, but in another level. Or it could be that Sora was an original Keyblade Knight, since the story is 10 years before KH1, before Sora was born.
Lol a nobody to a nobody? :D would definitely mix in. Well I guess we'll have to wait until release. It's hard to guess how the Kingdom Hearts world is ment to be.