Kh4 theory for you. What if we actually will be playing as 2 soras. Think back to kh3 which had 2 endings. sora crystalized by yozora the bad ending *which I still think is canon, and the official ending where you win. Yozora states knowing sora, and that our sora isnt it. In quadratum we see a sora waking up this could be the depiction of the good ending events play out and the sora in quadratum we see= the sora yozora knows or perceives differently. We also see sora passing out from seeing goofy&donald's vision appearance in quadratum. This "black out" could be how sora mentally swaps between a body in limbo via the disney worlds, and the current body in quadratum. Also its possible the memory is not shared by the 2 forms of sora and will only complete once they synchronize, which may also be what the box will assist with.
So essentially we will be traversing kh4 back and forth between 2 stories for sora. 1 being a vanguard/defender in quadratum, and 1 traversing the disney worlds