If we stay in the XII, I think we need to aggressively pursue Arkansas and LSU. As a conference, we blend better with those two border states then any other additions we could add. As rivals, Arkansas is already a former rival and LSU alums are in all parts of east Texas. If the big XII can convince Fox to build a network for them that rivals the SEC and the B1G, they might be able to convince those two to come on board. The biggest issue would be to convince LSU and Arkansas that they would have equal voices in the room, they wouldn't lose money and things would not just be all about Texas and Oklahoma. Playing on the Alabama controls everything in the SEC narrative might be helpful. I think both of those schools would thrive in a new Big XII, especially Arkansas.
If the Big XII was somehow successful in pulling of this coup, I would fully expect the SEC to go after West Virginia and another school to maintain their game inventory for ESPN. If West Virginia leaves then you go after Nebraska, Colorado or one of the Arizona schools.
NORTH
Oklahoma
Oklahoma state
Nebraska
Kansas
Kansas state
Iowa state
SOUTH
Texas
Arkansas
LSU
TCU
Texas tech
Baylor
Setup some permanent rivals that make sense and that can be a conference that last for a long time.