Of course THE Brian Kendrick can make it. Mind you, I've liked this kid ever since his days as Spanky... but the whole "The Brian Kendick" definitley has potential. However, like what has already been mentioned here is politics... and that would be the only thing stopping him from actually getting somewhere. But I reckon they should give him the whole "Climb the ladder and prove yourself" thing - where he's this arogant young kid who has nothing to show for, so he's challenged to win a title... so he goes out and wins the U.S title or something, and over the years he gets built up into a main-eventer.
Size? As far as size goes, I think if he has the charisma and talent (which he certainly does) then eventually size wont matter... and also, it may work quite a wonder for the WWE's outside reputation to not have a muscley, over-sized man at the top. Previously, that's what wrestling's been about - (look at Andre, Hogan, Goldberg etc) - but that was at a period in time where wrestling was more about competition. It's not anymore. It's about character, charisma, personas and ratings. Sure, it helps if youre a good wrestler (he might not be the best, but TBK surely isnt as bad as some) - but if guys like Cena can sell without having half the wrestling skill of TBK in my opinion, then it wont matter and Kendrick can sure as hell do it if he's given the right chance.
He has potential and right now the WWE's wasting it. I'm not saying, stick him in a title match next week... but the least they could do is try to build him up.