There is an argument for moving Illinois up and that would help Minnesota by eliminating their negative upset. As mentioned, Illinois is at +2. Moving them up into tier-6 would impact the projections for their home games against tier-5 teams:
I think there should be some hesitation as it relates to moving down teams in tier 1 or moving teams up in the bottom tier.
The simple fact is that when you're predicted to win almost all your games, there almost zero opportunity for positive variance. When you're predicted to lose almost all your games, there's almost zero opportunity for negative variance. But good teams have the occasional bad day, and bad teams have the occasional good day.
And it's especially true that a lot of the weaker teams in the B1G don't lack talent. They often are young, have coaching issues, etc. But Illinois recruits good players. When they have a good day, they can knock off almost anyone and it's an "upset", but when they have a bad day, none of their losses are "upsets". Whereas I think Wisconsin at one point this year was even with +2 and -2 variance. Their inconsistency meant their good day could be an upset, but since they were in the middle, their bad days could also be upsets.
So while we generally consider +1 or -1 as "on notice", I think for a team like Illinois one should be very slow to move them up, even at +2, unless their play on the court actually looks like they're putting it together.