Something that might be kind of cool for the next KH game, just to at least justify making Sora either a big whore or so, a Body Form Switch mechanic. With the push of a button, Sora can switch out his body with Xion or Roxas and for an unlockable, switch out with Ventus/Vantus/Veantus, and each one plays differently. Sora can use Drive forms, Xion can use Memory forms, Roxas can use Nobody forms, and depending on the unlockable, use the command thingy that he's associated with or something. Memory forms can be the forms Xion used in 358/2, and Nobody forms can be reminiscent of various Nobodies from KH2 (like Axel, Xigbar, Saix, Vexen and Larxene, with each form using a special version of the spell associated with it), and all the form types can use the Drive gauge like before, and throw in one or two new Drives for Sora and maybe a new one for Xion and let Roxas use the kick-ass form he had in 358/2 and KH2 went he was fighting Sora or Axel.
And is it me, or does Demyx look a little bit like Travis Touchdown with his mugshot from 358/2?