Let's break it down into three segments, which I think will give us a better understanding of a realistic look at the schedule.
Should win:
MTSU
USD
NIU
Coin flips:
Northwestern
Purdue
Michigan St
Illinois
Upset specials:
USC
Wisconsin
Penn St.
Ohio St.
Iowa
Now, if you are willing to accept the premise that most teams will win the games they should, and split the toss-ups, that puts us at 5 wins.
If we overachieve and win all 4 toss-up games, that puts us at 7 wins.
If we manage to defeat, say, 2 of the 5 teams that will be heavily favored, that puts us at 9 wins.
Therefore, an "acceptable" range of victories should be 5-9, with 6 or 7 the most likely outcome.
Now, since 6 or 7 wins is the most likely, and a 6-7 or 7-6 record is, by definition, mediocre, how can you sit with a straight face and lambast people for "excusing" mediocre records?
You can live in fantasyland, or live in reality. I, for one, choose to change the things I can, and accept the things I cannot. Those of you living in fantasyland would like to think that holding Brewster to a utopian standard of achievement will somehow will this team to 10 or 11 victories. But here's a newsflash: this team has been mediocre for 42 years and counting. No one outside of Nick Saban or Urban Meyer was going to come in here and lead this program to Rose Bowls within 3 or 4 seasons.
Generally speaking, most teams will finish within 1 or 2 victories of where they should. By that standard, Brewster should be commended for finishing with 5-8 wins. Anything less than that, and he should start polishing up his resumé. Anything more, and they should erect a statue of him outside TCF.