You made some additional good points.
Texas and Oklahoma in the SEC would be strategically powerful for the conference. Both may be experiencing a metamorphosis in attitude from separate angles, but admitting it would be difficult for them. If they moved together whenever the moment allows, that would provide added comfort and rationale without the face-saving baggage. Texas A&M, Mizzou, LSU, and Arkansas are in the SEC. They are strong and solid neighbors. It makes sense logistically, economically, and practically. And playing schools such as Alabama and Auburn regularly have high national meaning. All that would make the SEC more mighty and probably very good things for Oklahoma and Texas for the long-term, but the fallout for schools such as TTU, oSu, KSU, TCU, Baylor, etc., would generate some not so pleasant discourse.
While the B1G is a great conference, it is geographically awkward for schools in the southwest. The PAC12 could have had a TEX-Okie focused division several years back, and those talks failed. While the other four P5 conferences have bordering and moderate overlapping markets, the PAC12 may think they are immune to geographic hegemony by others onto their turf. Really, only the B12 could feasibly move westward, and they have written that off as an option.
I don't know if the SEC will find an avenue to penetrate the NC-VA domain with a current ACC school. Yes, Slive had that as a goal. I do believe the SEC may have a future shot at NCSU if a Texas A&M-style situation develops there. ND full-time in the ACC, drop one ACC school in NC, and add two such as WVU and UConn, or maybe even Cincy, could be a winner for the ACC if 16 all-sports is the goal.