Big areas like the treehouse in Deep Jungle. Large enemies that you have to climb to fight; ie: Rock Titan, Darkside face, Behemoth
Sidequests like trinities and Dalmations
This is a stretch, but online co-op, (jump in as Donald, Goofy, or really anyone the story makes optional) like, imagine comboing the same enemy with magic and combos at once.
Enemy flinch animations, that'd be appreciated. We've been kinda snubbed outta these through BBS and DDD, especially with human enemies such as Ansem. One of the great things in Kingdom Hearts was the fact that in duel type battles, (Clayton, Jafar, Captain Hook, Riku, Ansem, the list goes on) your enemies felt more real, because they truly reacted to taking damage, similar to yourself. In DDD I beat the ever-loving shit out of Ansem and he just stands there, grunting in pain until he counters. Feels kinda fake.
Also, can we have our intuitive Sora from Kingdom Hearts back again? I miss playing as someone who isn't mentally handicapped.
And this one's a crazy stretch, but maybe an option to transform into Sora from KH1, KH2, and DDD at the beginning of the game (or at will)? It could really change your playstyle and add replay value.
OHANDIWANTSOMEBETTERDISNEYWORLDSILOVEDISNEYSOMUCH