Well... It would be awesome if they could get Kefka a spot, maybe like an extra boss like Sephiroth in KH1, except he'd probably use more odd battle tactics. If it HAD to be a good guy, i'd have to say... Gogo. I don't know why, but I just happen to really think Gogo is cool. And if not Gogo, then Quina. (cause Quinas funny.)

What would be even more awesome would be if they could fit in the FF5 Gilgamesh as a boss. (He's my second favorite GENERAL [evil/good/whatever] FF char., next to Kefka.)