Or the main antagonist before the Xehanort saga , who knows?
No, i don't think Luxu pretends to be MoM. Ava would call him MoM if he told her he wasn't Luxu ?
Nope because "Why would he do another Keyblade war after seeing the first?"... that's the question!
Edit : Except if he is a psychopath? Or because he think it's fun!(PSYCHOPATH! )
Okay, it's stupid "Xehanort want to see what happen after a Keyblade War." in short. Soooooo... Why did you think it's him again?