If they can't get Texas for the ACC, my pipe dream would be Penn State leaving the Big 10 and rearranging the divisions along more traditional NE football and Southeastern football lines.
Absent that, the next best choice, from my perspective, would be the Navy / Georgetown hybrid model. Great name for basketball, and one of Notre Dame's signature football opponents. That would be a win-win, if you can't get Texas or Penn State.
I know that SWC also brings this up from time to time. But just imagine this football league:
North:
Notre Dame
U Miami. (What a rivalry they used to have!)
Penn State
Virginia Tech
Syracuse
Pitt
Boston College
Navy
South:
Clemson
Florida State
Louisville
Virginia
Duke
UNC
NC State
Wake Forest
The rivalries would be SO much better! Please please please.