They would be a better fit than ND since they have a stadium that holds 100k. Texas only has 2 rivalries and they can still play in Dallas against Oklahoma and play thanksgiving nights against Texas A&M.
I don't like Missouri at all as an addition, but it would be nice if the Big 10 was more sought after to the point that a big 12 team wants to join the Big 10.
Just to purely spite Ohio St, I want to see Cincinnati join the Big 10. Cincinnati is close enough to all the schools that if they ever expanded their stadium, they could consistently sell out 60,000 a game. PSU, Tosu, Mich and Wisc would all bring their fans en masse and fill up.
I always think about potential big 10 championship sites, it seems like only Houston, Dallas and Kansas City are Big 12 host cities for football. In the Big 10, we have Minnesota (The vikings will probably get a new domed stadium in the future) Heinz field, the stadium in Philadelphia, Ford Field, Soldier Field, or even the dome in Indianapolis. If we must, we can consider the 2 Ohio pro stadiums as well.
One nice thing about a Big 10 title game, anyone can buy tickets early and make plans well in advance to attend.