This sounds odd, but I'd make beginner mode a little harder. I figured since I never got far in KH1, that'd I'd try beginner mode. Big mistake there...I literally had no difficulty throughout the game. Even if a person never played the KH series before, come on, I had hardly any experience and I still thought it was simple, including the final boss.
I'd get rid of Atlantica. Sure, I'm pretty sure I had heard Sora's voice singing a few times, but there was nothing there really. Then you'd finally get somewhere, then it'd be "You need *insert requirement here*!" And then by the time you get it, you're like, "What happened last time?"
Sora's HP...it was really decieving. You could think that you're really low on HP, then bring up the Status screen and your HP is pretty high. Wasted a lot of potions...And, it felt like he was getting more HP every battle. Sure, HP is a good thing, but it always felt like he was gaining too much too quickly.
And last but not least, Reaction Commands. It felt like you were using them 24/7. Oh no, Nobody behind me! *Reaction command* Sure, I liked the variety it added to the battles, but it felt like it was too much at times.