BYU could compete with Wisconsin if BYU is dramatically improved, Wisconsin overlooks the game, and we get a few breaks. I believe that Washington sometimes plays down to their competition and a typical BYU team could find a way to pull off the upset. Utah may suffer some injuries and typical November struggles and a miracle could happen. Boise State may finally return to earth and BYU might finally get a game on the blue turf to go in their favor after three 1 pt losses in Idaho.
On the flip side, USU & N Illinois both have byes prior to coming to Provo and should be well rested and prepared. BYU could overlook McNeese State (who seems to be decent) and start the season with an 0-5 September. UMass has already shown they can beat BYU and this game will be on the road.
BYU shouldn't start worse than 1-4 but beating Arizona or Cal or Washington or Wisconsin will be very tough. With significant improvement BYU could upset Arizona or Cal but going better than 3-2 is less likely than my retiring this year. I believe starting 0-5 is more likely than 4-1.
Realistically I don't think BYU will go worse than 3-9 (worse case scenario) but I don't believe they will go better than 8-4. If I had to bet, I would predict 5-7 (losses to all P5 teams plus Boise St and USU or N Illinois).