So in an expansion effort, I'd like to see the SEC only add Texas and Texas A&M, or Texas and Oklahoma.
In that instance, you go to 14 teams. 16 is too many and harder to deal with for scheduling. You'd add the new additions to the West. You'd move Auburn and Alabama to the East, since 2 of their big rivals, UGA and UT respectively, are already in the East. Then you move either UK or Vandy to the West. Division splits go this way:
West:
Texas
Oklahoma/Texas A&M
LSU
Arkansas
Ole Miss
MSU
Vanderbilt
East:
Tennessee
Georgia
Florida
Auburn
Alabama
South Carolina
Kentucky
In football, you could still play 1 permanent from the other division, and I'd split it this way (Florida-LSU, SC-Arkansas, Tennessee-Vandy, MSU-UK, Ole Miss-Georgia, Auburn-A&M/OU, Alabama-Texas).
That's assuming you'd want to do any permanents. If you don't want to do permanents, you play 6 division games and 2 rotating games. If not, you have 6 division games, 1 permanent, and then either 1 or 2 permanents depending on whether you want to go to 8 or 9 conference games. I think the ultimate decision would be to go to 9 conference games. It's more attractive for TV deals to have more conference games, so I think 9 may be the future if expansion comes.
The nightmare scenario for us would be if they added Texas/Oklahoma to the West and then two ACC teams to the East like FSU/UNC to go to 16 teams. Having Texas, OU, Auburn, Bama, and LSU in the West would be awful for us.