There are a lot of different directions that this thing is being pulled into, which it makes sense why they're deadlocked.
They only need a simple majority of 6 out of 11 votes for the new contract (starting in 2026), but it also has to be 3 out of 5 of the P5 votes. So the "Alliance" can block it, without one of them breaking off.
What size/format - SEC wants 12, so they can get more teams in each year, 8 is a nonstarter for them. G5 wants top 6 highest ranked champions, autobids for P5 is a nonstarter for them. Alliance wants P5 autobids (which would be greatly in the new Big XII's interest as well), so that they can't have years where their champ is left out for a Sun Belt team. And while 8 could seem more wieldy, how do you satisfy everyone? Top 5 champs + 3 auto's? 5 auto + 1 top G5 + 2 auto? Neither of those would seem to work.
Scheduling/logistics - Obviously though, a 12 team bracket takes 4 rounds. The first round or "play in" round gets you down to 8, which then takes three rounds. You have the NY6 bowls, which could be quarter and semi finals each year, but what would be the schedule? Shouldn't the Rose bowl (and perhaps Sugar) always be a semi? Would the other bowls agree to step backwards a week back from NYD, then? Or you could have quarter-final bowls on NYD, and then which two bowls step forward a week for the semi-finals? Or do you bid out from the semis onward?
Another issues is the first round games. Should they be home games? Or should they be played at bowl games? The issue with home game is like this: the four losing teams basically get jobbed. Think about it: you're the undefeated Sun Belt champion, ranked in the teens. And your reward is ...... traveling to College Station, TX to play A&M (at-large) in a defacto home game for them, lose, and not even get to go to a bowl game or bowl game atmosphere. Who wants that? But if you have the first round be at bowl games, which bowls and what would be the schedule?
Rose Bowl - this is a whole issue unto itself. The Big Ten, PAC, and Rose view this property as a special thing that is on the level of the CFP itself. Like the Kentucky Derby or the Masters. They want to do everything in the power of the universe to preserve this property as a Big Ten vs PAC matchup and on NYD afternoon timeslot. But they also don't want it to get overshadowed by the CFP. Ideally, it should be in the CFP, while attempting to preserve that matchup. This is also part of why the Alliance wants P5 autobids.