Ok, let's imagine how that'd look. There'd be two play-offs. One with the majority of fans and viewers and the other with fewer, but bigger media exposure. How long would it take for the mighty to jump in to the media ring? Remember: in terms of financials the biggest media players are still on the outside looking in. IMO, not very long before Apple/Amazon/Google/Meta start ponying up more. Plus at a low buy-in. I see the B1G/SEC split as being a major bust. Of course, just my opinion.
You would have two playoffs with the "major" schools in one, and the smaller schools from the rest of the country in the other, when looked at by success and name recognition. The B10 and SEC will be shown on the two dominate sports channels, ESPN and Fox. I looked up the numbers for MLB looking at their Friday Apple numbers compared to their Sunday night ESPN numbers, as a comparison. ESPN has the higher rated numbers. The idea that vast numbers of people will turn away and not watch, is silly, a large number of those people are not going to watch anyway. So it will come down to the people that care to watch sports, most of them are in the footprint of either the B10 and SEC, the ones not that are in cities like Dallas or Houston in the B12 or Miami in the ACC could care less about sports, or are professional sports fans.
As much as we would like to tell the B10 and SEC to shove it, and leave, by doing so, we would also sink. Both conferences could expand and add a few more teams, and sink both the B12 and ACC, if they wanted to do it, and there is not a team in either conference that would not jump at the chance to join either league.