It would be a huge game, and if BYU won it would be on one of the most significant games in the last 30 years for BYU. A win against Michigan would give BYU legitimacy in the NY6 discussion (and possibly push them into the playoff).
It seems like you're straw-manning the scheduling argument that many on this board are making. People advocating for an easier schedule aren't trying to duck each and every P5 game - they just want a thoughtful schedule that isn't front-loaded (killing momentum, media attention, and depth) and that is commensurate with the resources that the school has. A team can recover from late-season losses (look at Utah's final ranking last year, even though they imploded against Oregon and then Texas), but they can rarely recover from a slow start.
And I think the Boise St model is ideal. You don't get respect for losing against a tough schedule, but you do get respect for taking care of business and winning games. For the first time in a long time, BYU is 6-0, ranked in the top-15, and people on CB are talking as if BYU could beat any team outside the top 6 on any given Saturday. BYU's QB is a Heisman dark-horse, and people legitimately think that BYU deserves a NY6 slot. None of that would be happening if BYU had multiple losses, even if those losses were to P5 teams.