Marquette fan here, from Kansas actually so this realignment is hitting me extra hard. The problem with thinking that the Beast can just add KU, KSU, Mizzou, Memphis etc ignores the fact that the B1G, SEC & PAC have to find enough teams to get to 16 as well. Where does the B1G go if Mizzou, WVU, Rutgers, Syracuse, or UConn is gone? Notre Dame is their dream but is their independence a threat yet to their ability to compete for championships? They'll only go if they see the 4x16 team conferences as the future of a pure playoff they may get excluded from. Mizzou would fit but they have to get to them before the SEC. Kansas and KSU become very attractive as well. Where does the PAC go if UT doesn't join OU and OSU? KU and KSU are next best options, unless they give in on their Sunday rule and let BYU in, maybe UNLV or Nevada.
The point is, there wont be a football-league with likes of Kansas to join with. You may get something like Memphis, Houston or even maybe UNLV if you could ever figure out geography, bu Kansas, Louisville, Cincy, Mizzou will all be in a fball-only conference.
Notre Dame staying in independent is the single most important decision for teams like us. If Texas decides to go Independent, this could actually end up pretty well actually, but they seem to want everything but independence to keep their LHN.