There isn't a rule that Mages can't use swords. It's unconventional, yes, but it can work and be interesting if done correctly.
I'll give it a quick read and edit this post with what I think.
EDIT: Wow, that was quick.
I could only stand to read the first couple of paragraphs before I lost interest, honestly. I mean, what the hell is up with Travis Town?
The conversations, from what I read, were bland at best. No humor or wit in them to say the least. Plus the fact that he chose to take a pre-exisitng story with pre-existing characters in them and adding fan characters would just lead to a jumbled mess of "Who the hell is supposed to be the hero of this thing?"
It would have been better if you took the Kingdom Hearts universe and made your own story within it, only including characters from the series in the form of cameos.
I might be a little harsh, but I honestly didn't feel immersed in the story in any way what so ever.
Take this as you will. Call me a harsh [Bumpity-Boom!] if you want to. Thems just my two cents.
And those "Before and After" conversations at the begining and the end? UGH.