Crouch, Frost, and especially Frazier would have been excellent quarterbacks in Frost's offense. Their ability to stress defenses with their running would have opened up the pass. The decision making, ball-handling, and football smarts that those guys possessed would have translated into a lot of good football.
Just as you don't need to run a 4.3 40, you also don't need to be a 70% passer. Crouch, Frost, and Frazier were asked to do different things, but it doesn't mean they would have been incapable. For what it's worth, in their final seasons each one of them averaged more yards per attempt and more yards per completion than NFL hopeful Tanner Lee. Each had a comparable passer rating as well (124 to 129 range), with the exception of Frazier. He blew them all away with a rating over 156. And Lee had almost no ability to run.
So yeah, those three would have been recruited and likely successful in this attack.