1st of all... I do NOT see Michigan being "man on an island" and being one of the few schools not playing. If the majority of B1G schools play, all of the SEC schools play, all of the Big12 play .... then I do NOT see Michigan as "odd man out" and not playing.
BUT .... let's just hypothetically say that does happen. Can you imagine the migration of players from Michigan to other programs that are playing. To 17-22 year old guys, 1 year is an eternity. You ask a 17-22 year old to sacrifice 1 year, and it's like asking a 50 year old to sacrifice 10 years.
I'd say every player on Michigan's roster who is in their final season of eligibility in 2020 will consider a hardship transfer. Yes, they could always petition the NCAA to come back in 2021, but again to 20-21 year olds, waiting a full year is an eternity. Why would they put their final season of college football on hold until 2021, when they can simply transfer to a school that is playing. How about the guys who would be entering their 3rd year out of HS and after this year would be eligible to leave early for the NFL. I'd bet those guys would not want to stick around and wait. They already had it in their heads that they would spend 3 years in college then go pro. They are not waiting until 2021, they'd transfer as well.
Again, I do not see Michigan going thru with this. I see them caving and falling in line and playing games. But if they do, this would have serious ramifications on their roster. Think of how long it took us to rebuild our roster from being short on scholarships.