The main problem is personnel. He doesn't have the DL personnel to get after the QB, so they tend to more frequently drop more defenders into pass coverage. I think if there was more talent on the DL, he would be more inclined to go after the QB and you would see a change in scheme. BYU needs to recruit better at the DL position. They have been able to stack the O well and improve the secondary, but the front 7 need to improve.
It is usually more about the Jimmy's and Joes than Xs and Os.