In my hypothetical you'd still be able to play cross division games, much like FCS and FBS play each other regularly now. So those schools could play UT or OU if all parties were agreeable. It's not like there would NEVER be games across those lines. I personally wouldn't give a shit, because there isn't a single school on that list that cracks my Top 5 most hated. My ideal schedule involves playing Iowa, KSU, Nebraska, Kansas, and after that I wouldn't give much of a shit. Most (not all) ISU fans feel the same way.
I also like the idea of 133 FBS teams and all the mingling across leagues. That lends the kind of variety that makes college football great. It also feels like a dying model as there's this groundswell to consolidate brands for TV purposes. On top of that, there seems to be a growing sentiment (and not just on this board) among fans of the biggest brands that games against lesser brands aren't interesting, and those schools shouldn't be allowing the lesser brands to essentially profit off their likeness. Those of us remaining in the Big 12 have been hearing it for a deacde.
While I initially found that sentiment insulting, I can accept that it's prevalent and real. If that's really how UT, OU, and other blue blood fans feel, then why shouldn't you be allowed to just play other blue bloods? The SEC and Big 10 are full of schools that aren't additive and have been grandfathered in. Cut them loose to play schools that are truly more their peers. At the end of the day, those 18 schools in the graphic are generally in a different league from a finances/talent/resources standpoint from even the other schools in their current conferences, who are much more similar to the current ACC/Big 12. There are absolutely some schools between 18 and 65 that have built their self worth around punking the big guys, but I think they'd find that playing in a setting with more parity and returning to regionality would be more interesting and appealing at the end of the day.