Knight is pretty athletic, he'd be able to move in a spread offense just fine. It's the whole throwing the football part that he struggles with at times.
Sumlin's greatest success as a HC has been with QBs that were coached by Kliff Kingsbury (Case Keenan and Johnny Manziel). Now he is looking at a QB that lost his job to Baker Mayfield (coached by Kliff Kingsbury).
IMO, Sumlin should pull out the full court press in an attempt to secure the services of Davis Webb. Sure Webb couldn't beat out Pat Mahomes at Tech but neither would Mayfield. If Webb's mind is set on transferring to Bowling Green then so be it but the effort should be made. Maybe Sumlin could get back some of that Kingsbury mojo and save his job...for now.