Did you seriously just say that he would not be a clone because of his speed and size? Have you ever even played Melee? Do you even know what a clone was in that game? Ganondorf/Falcon were clones. So were Mario/Dr. Mario, Falco/Fox, Pichu/Pikachu, ect.
Notice how I said moreso than any of the clones? That's beause I knew someone would get there. Okay. Imagine Bowser Jr. Looks like a Bowser clone, doens't it? Now put a curtain on him. He doesn't look like Bowser anymore! You can now give him moves based on speed, and of course the paint brush. And Shadow Mario as a Final Smash!
The moveset argument is old and false. It shouldn't be used agains or in favor of a character.
If you use the argument that he caused the events of plots, why can't you say that Geno was directly involved in the main plot and helped fix it?
True, but Geno never appeared in a mainstream Mario game, and didn't even appear recently (apart from a cameo that goes agains your argument on plot importance.
Anyway, as my blind grandfather said, wait and see. The leak isn't very far. We'll see who's right.