Difficulty wise, what KH4 needs is Critical Mode from the getgoWhat I love about all of this is the fact that the devs are hearing the community's complaints. "KH3 was too easy" - they added ReMind which is the hardest challenge the series has ever provided, just behind from the egg minigame from the bistro. "No FF characters & Kairi still does nothing" - they added them in ReMind and made her playable for the first time. "Too much Disney, not enough original content" - well KH4 looks like it's shaping up to have a decent mix of the two.
And now we have reaction commands returning and hopefully the end of those dreadful situation commands. The final product could be amazing.
Also I personally think Critical Mode shouldn't be some unlock after you beat the game once, I feel like you should be able to jump straight into critical