Simplified combat. As in, take it back to the KH1 formula. I can't stress this enough. I mean, in KH1, it never got much more complicated than continuous strings of Keyblade strikes. The big, flashy finishers, Sonic Blade, Strike Raid, Ragnarok, Ars Arcanum and Trinity Limit, were available any time you had the energy to use them, and when you did, you could see everything that was going on. You knew you were dealing out some heavy damage.
KHII was just... Messy. It started off well enough, but by the time you reach the end of the game, Sora's loaded down with so many different "special moves" and combo modifiers that you can barely tell what's going on when you fight. You're just mashing buttons, moving from one flashy screen-filling combo to the next. I think what happened here was that Square was less concerned with building a solid battle system and more concerned with building a battle system that felt cinematic, a point that's emphasized by the inclusion of "action commands".
If battles that look like they belong in Final Fantasy: Advent Children are your thing, more power to you... But if I had my way, I'd take things back to the way they were, when you felt like you had more control.
Also, no more pre-FFVII characters. It's not that I don't like these characters, because I do... It's just that I can't stand to see Nomura bastardize them any further.
Look at the other characters. Cloud? Basically the same as his VII version. Squall? Essentially the same. Cid? Notably less vulgar, but still essentially the same guy. So why did Nomura feel the need to completely destroy Setzer's character design and attitude? I mean, is it favoritism or something?
If Nomura is going to completely disrespect everything that makes the pre-VII characters awesome, I'd rather they not be included at all.