I did consider exactly that. What Duke came from is 27-13. They won the Coastal without him and barely scraped .500 with him.
Same goes for UNC. They went 11-1 and won the Coastal with a mobile guy who never even went to the NFL. Then Trubisky takes over and they drop back to 8-5.
Go look at Heisman winners over the last 10 years or so. Kyler Murray, Baker Mayfield, Lamar Jackson, Marcus Mariota, Johnny Manziel, RG3, Cam Newton. How many of those guys fit your big statue pro-style QB mold? Every one of them is short and/or mobile. Jameis Winston is possibly the only exception, but even he doesn't exactly fit the traditional pro style QB mold.
I'm not saying you can't win with a traditional pro-style quarterback. I'm saying you absolutely can win without one, and when you're running the spread, like we are, you may be better off with a mobile guy.