Well, I'm sure Sumlin won't want Manziel to be a total Vince Young clone. I agree, that doesn't translate too well to the NFL. Sumlin does want him to stick in the pocket and only use his feet when necessary, because those big SEC linebackers will lay some hurt on him if he tries running too much.
Give him a few years, and see what he does. I think he's got Heisman potential.