So, I'm not worried about him gaining the right kind of weight- muscle mass, and I'm not worried about him breaking down in college because of his weight. If I was a NFL scout, I might be worried about that at some point, but not in college. We have Balis, and I imagine that working with him, he will more than likely drop down to 260 or so and do the right things that he needs to do to maintain speed and manage his weight.
Think about all of the bigger QB's in college football in the past- Lorenzen has been mentioned, but then you have Duante Culpepper, Byron Leftwich, Relf I consider to be successful, JaMarcus Russell, Tim Tebow, Ben Rothlisberger, and etc. QB's that are large have been successful before and will continue to have success in college- moreso than tiny QB's. And I'm calling a big QB someone over 230 pounds for reference.
Also, as far as speed- a guy like that is just like Relf. Relf was not very fast, but he would run over you and punish you. I don't know how fast Tebow is, but he definately will punish you as a runner. I think Liggins could be the same type of QB as a runner- someone that will use his size to run over people and gets yards rather than outrun them like a Micheal Vick.