BYU really would need to go 6-0 at home and then 3-3 on the road. This would mean that at the very least BYU beat either Mizzou, Nebraska, UCLA, or Michigan, and then beat SJSU and Utah State on the road as well.

8-4 is a success if BYU wins one of its Power 5 Conference Road games.
9-3 success (probably finish the season ranked or just outside the rankings)
10-2 Bronco Haters will have to shut up.
11-1...Top 10 ranking, NY 6 Bowl game likely.
12-0 Top 5 ranking, Outside shot at the playoff...Not likely but it would throw a huge wrench in the works.