This. It's actually very similar to an idea someone here had that stuck with me about having a game like 3D or BbS, where there are multiple scenarios, but with one scenario being TAV, another being Riku and Kairi, another being RAXIN (sorry, I was saying RAXI to include Isa and now I have to include an N for Namine, lol) all looking for Sora. I would really love a game like that, especially if they let you choose which character(s) to play as or switch between characters while in each separate scenario (for example, choose to play as Riku or Kairi for that scenario, choose to play as Terra or Aqua or Ven in their scenario, etc.)
Well, with the announcment of Project Xehanort, I'm thinking the Xehanort saga is not at an end, disappointingly.