Either scrap 100 Acre Wood entirely or actually give it more than 5 minutes of content. "Oh our bonds are fading, why is that?" And then nothing. One minigame replayed 3 times. No Eeyore, Kanga, or Owl. Yet Lumpy was there for whatever reason.
Option to turn off Attractions, or at the very least make them fade outside of battle. I enjoyed them, but they were far too annoying when popping in boss battles. Fighting Anti-Aqua in the Dark Margin? SUMMON SHINY BOAT!
Reflect magic, or at least an option for a 360 barrier block.
More original keyblades. I enjoyed the Disney ones, but not having any original ones besides Starlight and Ultima (that I know of) is kind of a bummer.
Pacing. Not 8 Disney Worlds with a small pinch of baddie dialogue mixed in and then 6 hours of finding guardian after guardian and then promptly dying and then jumping into the final clash. Put saving one of them in the middle.
NOT SHOWING EVERYTHING IN THE TRAILERS. Too much was shown. Absolutely too much. Nomura made it seem like there was so much more left to be seen, but the only thing we never saw was whatever happened after Master Xehanort said "Scala ad Caelum".
I still loved the game regardless and feel so empty knowing Sora's fate. But it certainly had its faults.