actually worked out pretty well for BYU because it was a clean cut for those who served missions.
My uncle played quarterback for BYU as a freshman in the 60s, and I'm pretty sure he actually played on a "freshman team," which would have been separate from the JV. Maybe I'm wrong and it was actually the JV team.
Anyway, the point is the freshmen could play at some level. This move by Boise State is unprecedented.