I think my brain has peed itself after reading all of this. But now I raise another question. What happens to shell's when the heart goes back, like with Sora. Does it disappear, that seems to be the likely option, but we don't know. But I honestly think Roxas is a normal, who has just had his memories messed with. Because the way I see it, if you have someone else's memories, then wouldn't that make the 2 people similar. So if the original person's heart was strong enough to be a keyblade weilder, then by default the one who's memories were manipulated to have some of the other person's memories then would their heart be strong enough to weild a keyblade? Even though I'm sure that is completely wrong, I still don't think Roxas is Sora's shell b/c of what this says **SLIGHT SPOILERS IN THIS LINK** http://www.khinsider.com/news2/headlines/137033974.shtml
Look under general info part and read the second point.
Look under general info part and read the second point.