Anyway, I got a really cool idea from someone at KHU:
What if in KH2, you could take the Twilight Town Train (Which goes to Yen Sid's place in KH2, which was in some kind of fantasy realm or something) and take a trip to Castle Oblivion (If you look at it, Yen Sid's place and Castle Oblivion have a lot of similarities, which leads me to beleive they are near each other) and since we all know that Castle Oblivion is the place of Memories and Finding/Revisiting your Memories, when you go into Castle Oblivion you can travel up the various floors and every Floor allows you to access a memory of a Boss you previously fought, so you go to Castle Oblivion and in there you can fight all the COM Bosses in a full 3D battle
Just thought it sounded cool =\