Don't think that his size/obvious power potential should be a variable for whether he could be a character. Think about it. They put Mewtwo in Melee and he was the worst character!
That's true I guess, but I just can't picture him being playable. Shields in Melee were all the same size, regardless of the size of the character using it (which is why bigger characters are easier to hit through their shields). If Petey was playable and if they keep shields the same way they did in SSB and SSBM, it wouldn't be useful at all.
I don't know though. It is a new game after all and things might be changed around a lot.
I hope his jetpack and pistols make a return. I mean they're in his rap and everything (and shut up about dk's lack of coconut gun that fires in spurts :x).
I haven't played the game this Diddy's from (I'm assuming it's the old N64 one), but isn't his jetpack the Rocketbarrel Boost and isn't his pistol the Peanut Pop Gun? Or are those two completely different things?
Diddy looks like he'll be a pretty tricky character, since he has that "whimsical" fighting style. I'm glad he's going to be somewhat different.