Vick played the QB position, but you've clearly got your head up your ass if you think he is a plug and play for Donovan McNabb. McNabb is one of the most underappreciated QBs in the game, he's not the QB he once was, but he can run the position far better than Vick will ever be able to.
Anyways, I don't think they plan on playing Vick as QB. He's been out of the league too long to play QB with any kind of consistancy this year. I guarantee if Vick gets consistant playing time it's going to come out of the Pro Set formation with him and Westbrook split behind McNabb, and any kind of throwing he's going to do is going to be from pitches/screens with an option to run/throw.