The Pac-12 and B1G would Texas standing alone. Oklahoma would require one of those partners in the top 100 research schools (KU or ISU). After you trip those three schools, the rest are stuck. Texas could possibly dictate Tech, but that is the only 2nd group outside the top 100 who could get a lifeline.

I see 5 schools stuck in every scenario, and 1-3 more likely stuck. Is Iowa State or Kansas worth enough to consider without Oklahoma or Texas going with them?

It should be remembered when Oklahoma pitched to the B1G back in 2011, as a group of 5, they listed Nebraska, Iowa State, Texas A&M, and Kansas as the other four. They are all your first tier R1 and top 100 research schools. Further in 2011 all except Oklahoma were AAU members. I think that should put to bed any notion that Oklahoma is glued to Oklahoma State. Note, another way to look at it is the rumor was a fabricated one, a trial balloon for the other conferences knowing that Nebraska joined the B1G, Texas A&M the SEC, and embedded in the rumor was Missouri having already decided to maneuver for the SEC and Texas not coming with Oklahoma. When you filter that, the rumor says OU would be willing to go to another conference, and it's acceptable to select KU or ISU as their partner instead of OSU. Personally I think that is what that story is really about.