Not to hard to name a plausible six adds for the SEC. That contraction by eight down to 12 again is a little tougher. I think contractions would evolve historic powerhouses breaking from the SEC. The contractions could therefore be less than 12 initially. Anyone very familiar with the inner gears of reality in college football knows they are often headstrong to what best benefits themselves.

The ADDS to 20 would be FSU, Clemson, VT, Oklahoma, Okie Lite and a Texas school, either the Longhorns or Texas Tech. I don't see a Texas church school or any team named Jayhawkers ever in the SEC. Perhaps another ACC schools could be the #6 or #20..

On future contractions in several later decades. I could see Alabama, Florida, Auburn, Tennessee, Georgia, FSU, Oklahoma & Texas breaking from the SEC to form what they would call a Super Conference with their own TV deals and no NCAA oversight. The remaining 12 SEC members might break off to their old alignments or they could form a 12 team with two divisions like the old SEC.