Well, for themes I'm guessing obviously one of the themes should be about the main themes there are in KH: friendship, the heart, the Keyblade, Kingdom Hearts, etc. And then maybe some themes of your own that you may wanna add, like maybe darkness or something. And as for the Keyblade wars thing, what do you have in mind for it in your story? I'm thinking Kairi's Grandmother's story is honestly connected to it, seeing as how Master Xehanort even hints at it. I dunno, that's just what I think.