So here is my wish list:
1. I'd like for Forte the pipe organ to appear as a boss in a return to Beast's Castle. He seems like he would be fun to fight against. I'll bet they can come up with some cool combos against him like swinging on his pipes and slashing at the the keyboard with the keyblade. Fife could be in the background cheering you on and giving you hints on what to do to defeat Forte. He would also be cool as a summon afterword's. He could attack with a bunch of different music combos.
2. The Emperor's New Groove. It would be cool if you could steal potions from Yzma's lab and have the ability to turn into selected animals in that world. Kronk would be cool to fight against as a mini boss. Cuzco, of course, would be joining the party in this world.
3. A Bug's Life. I think the plot of this movie would be perfect for a Kingdom Hearts game. Hopper and his gang seem like they would be able to work well together with the heartless. Sora can be an ant, Goofy can be a beetle (kinda like Dim), as for Donald, he could be a butterfly. Flik would be fun to have in the party. He could perform limit attacks with his various inventions, like the one he was using in the beginning of the movie.
4. One character I was really disappointed not to see in Atlantica in the first two games was Chef Louis. They should have added the castle as part of the level. Louis would make for an epic mini boss. I can just see you dodging knifes, forks and other kitchen equipment while trying to protect Sebastian at the same time.