Would it be cool if they put a secret boss character in the next Final Fantasy that is from Kingdom Hearts like Xemnas or any other character?
This would be great and funny, but isn't it more likely the next FF boss will be put into KH? However, then I would buy the next FF.
It would be a good idea but it must fit into the plot somehow and not just throw them in. Sephiroth in KH2 was an excellant example of how how to put a chracter in while making sense. I also read on wikipedia that Seymour Guado (From FFX) may be an optional boss in the next KH game (more likely the one that has Sora in it).
I don't think that that would go with the whole realistic aesthetic that FF games waver towards, it would be pretty cool if they did do it though...