It's hard to say exactly how much home-field advantage is worth, but BYU does play a LOT of their P5 games on the road - definitely to their credit and also to the detriment of their win percentage. Honestly, I'm not going to go back and look at all the data for that, but even with the bad home/road breakdown, they're already comparable to a low-level P5 team. Maybe accounting for that would bump them up a bit.