I suspect the B1G to forego divisions fairly soon; they didn’t go to divisions until 2011.
The ACC went to divisions once they expanded to include Big East teams.
The PAC-12 didn’t include divisions until 2011 when they expanded.
However, they all followed the SEC Model. The SEC have been using divisions since 1992. I know w/ the expansion to 16 in the next coming yrs, the talks have included to scrap that tradition. The B12 is now considering divisions once they expand to 14 teams before UT & OU leave, & talks r they’ll keep divisions when UT & OU leave.
In the PAC-12 & ACC especially, it makes sense for to scrap divisions b/c frequently we’ll see the best teams play in the same division, but only the division winner move on. How often have we seen The Coastal send up a sacrificial lamb for the Atlantic since 2004? Since SC has been down most of this time since 2011, how often have The South been a sacrificial lamb for The North?