This so idiotic it isn't funny. You picked the ONE guy that you can say did the same thing you say Weisman will do. Because he did it, your argument is that Weisman will do it. I would be willing to bet (here i go again) that if you went back in the history of college football there are guys like Weisman all of the time that play at a very high level in college that don't get a sniff in the NFL. But your case is so weak you can't be shot down by anything logical because you don't present logical arguments.
Why stop at Alstott? Why not say he is Jim brown? That was another fullback type that had huge NFL success. But you won't make that case because it is a stupid case to make.
Larry Csonka, Daryl Johnston, John Riggins, Tom Rathman, Robert Newhouse, Toby Gerhart. Many, many more.
Don't discount Weisman. Would not surprise me at all if he ends up on an NFL roster someday. (would not surprise me if he didn't either)