For purely objective reasons and not accounting at all for the fact that my team might be one on the chopping block...
...I'm against expelling members.
I am as well, but upthread or in one of the other threads someone asked about how things would be different if you were making the conference today.
In that vein, I think that Northwestern probably wouldn't be in the B1G. They are a charter member from way back when the league (especially before the Lake Forest/Michigan switch) was basically a Chicago Metro Area league with a few nearby large state schools (IL, UW, MN). At chartering the league had two schools in the Chicago area (NU & UC) and at the pre-charter discussion meeting they had three (NU, UC, and the aforementioned Lake Forest).
Northwestern definitely made sense when they were one of three Chicago-area private schools. They made sense at chartering when they were one of two along with the University of Chicago. Ever since Chicago quit (going on what, 80 years ago) Northwestern has been the odd team in the league. The other 13 are all large state schools. Per wiki B1G member enrollment ranges from 61k for tOSU down to 22k for NU. After NU the next smallest schools are UNL (25k), IA (30k), and UMD (41k). The median is between #7 PSU's 45,901 and #8 PU's 45,869 so Northwestern is less than half of that. Additionally, they are a second school in the state of Illinois which isn't really necessary which brings me to . . .
After Northwestern the next two on the list to not be members would be MSU and either IU or PU. Nothing against the Spartans, Hoosiers, or Boilermakers it is just that the conference doesn't really need two schools in Michigan or Indiana either. NU, IL, and PU were all charter members while IU was added shortly thereafter (1899) and MSU was added in 1950.
In the 1900 census (around the time the league decided to have two IN schools (IU and PU) and three IL schools (UC, IL, NU) Indiana and Illinois were the 8th and 3rd most populous states respectively with 3.3% and 6.3% of the total US population.
In the 1950 census (around the time the league decided to have two MI schools (adding MSU) Michigan was the 7th most populous state with about 4.2% of the total US population.
Today Illinois, Michigan, and Indiana are the 6th, 10th, and 17th most populous states with 3.8%, 3.0%, and 2.0% of the total US population respectively.
For the reasons that YOU elaborated previously in relation to Iowa/ISU and Kansas/KSU the three remaining schools after you kicked out one each of NU/IL, IU/PU, and M/MSU would be stronger.
Also, it makes sense for the SEC to have two Texas schools because Texas is the second most populous state with almost 9% of the total US population. That was somewhat true back when this league decided to have two schools each in the (at the time) 3rd, 7th, and 8th most populous states which (at those times) had 6.3%, 4.2%, and 3.8% of the US population. It makes a LOT less sense now that those three states have a combined total population roughly equal to the state of Texas. Ie, the B1G having two schools each in IL, MI, and IN would be equivalent to the SEC having six schools in Texas.
So I'm against kicking schools out as a general matter but if we were doing it (or found that we had to) the schools on the block would be NU, MSU, and either IU or PU.
Now the question of which IN school it would be is interesting. Purdue was a charter member but Indiana joined in 1899 so it is not like they are some Johnny-come-lately. Also, Purdue has a larger enrollment but the difference is not significant and the two schools' endowments are also similar in size.
The obvious advantage of not having two schools each in IL, IN, and MI is that you could replace them with three schools from other states and thus increase the footprint of the league (ie, increase the size of the pie without cutting it into more slices).