Central Florida and South Florida.
End of discussion.
cf
I support expansion with Central and South Florida. It might not appear as attractive as some of the other options at first glance but a longer term perspective dissipates these concerns rather quickly when you consider the biggest restriction to both schools presently performing at a high level in both basketball and football has been recruiting. Becoming a member of a Power 5 conference should enable both schools to enhance their talent levels significantly in short order.
Additionally membership in the B12 should increase each schools athletic revenue by more than $15 million dollars which would further enhance recruiting success with the larger recruiting budget available to each school and perhaps all both athletic budget eliminate operating at a loss.
Don't forget the Central Florida has beaten both Georgia (2010 Liberty) and Baylor (2013 Fiesta) in bowl games recently. Since Jim Leavett left South Florida has not been as successful on the turf as has UCF but the did beat Clemson in a 2010 bowl game. Facility wise USF plays in Raymond James Stadium they share with the Tampa Bay Buccaneers with a 65,000 capacity and UCF plays at Bright House Network Stadium that seats 45,000.
Neither school has shown any consistency in basketball but that too should significantly improve with membership in the Big 12 and both schools have 10,000 capacity arenas for the sport. There is local talent available and now both schools would have a strong story to sell to prospects.
Florida is the third most populous state with 20.3 million people and population means TV set and TV set mean TV athletic revenue. The added Florida TV sets increases the total for the B12 by about 52% and that is a lot of additional revenue for all conference teams. Even with the addition of Florida to the B12 our population base of 59.5 million will be 9.3% less than the other 12 team conference Pac 12 (65.6 million) population and 33.3% less than the 14 team B1G (89.1 million). The SEC has a population base of 95.5 million and the ACC 97.6 million.
Lastly adding two Florida schools to the B12 would insure that every B12 school would play in Florida every year in all sports and that should allow every B12 school to improve its ability to sign Florida H.S. kids and that will make for a stronger league in all sports.
Personally I do not see two other schools that could bring nearly as many benefits to the B12 as could UCF and South Florida.