I think ideally if you add teams from the BIG 12 you would probably want to bring in Oregon, Stanford, Arizona and ASU. I could see a case for Washington, Utah and Colorado but the B10 already has teams like them and you could oversaturate the conference with mediocre teams. Right now the B10 has a problem with only about 5 teams at most being competitive and really only 1 or 2 being nationally competitive talent wise.
Assuming the B10 is able to add ND and Miami that should be enough from the east and south east but I think a case could be made for Virginia and Virginia Tech. For the two Virginia schools that would give Maryland a few games where they don't have to travel all that far and somewhat for Rutgers also.
I think ideally the B10 adds another big market in Miami and then get Oregon, Stanford, Arizona and ASU. That gives you a rather large TV market which would play in to the B10's TV plan making it more lucrative to be signed. This would give the B10 TV spots for East, Central, Mountain and Pacific basically covering each viewer base. This should then get the B10 to their $1 billion+ price tag that they are looking for. Basically this gives the B10 the ability to sell 3 time slots on Saturday where national TV providers really don't have anything on at those times. Football still sells and College Football isn't really that far behind the NFL in popularity.
I still believe this is 100% for TV revenue and will make AAU membership a small selling point. Getting a piece of that $1 billion+ revenue is what presidents of universities are going to be looking at as it will be a guaranteed revenue stream.