I would first find out if there is any interest from current Big 12 members Central Florida, West Virginia and Cincinnati. These programs are solid, provide traditional regional rivalries for current ACC members, have high levels of fan support, and provide good TV markets., especially Cincinnati and UCF. I think these programs could be very interested in being in the ACC even without FSU and Clemson. Regionality matters and they could very well take the opportunity if given.
Tulane is rising, has excellent academics, Top 50 national university by US News & World Report, and has New Orleans TV market and regional interest. They have a $2 Billion endowment. Road trips to New Orleans would be fun. The football team finished 12-2 ranked #16 in the country last year. The program is on the rise and is definitely worth considering for future expansion. Excellent opportunity for regional competition and developing rivalries. I think Louisiana is as far west as the ACC should go.
Navy Tradition rich football, national audience, service academy with top notch academics, Regional competition and rivalries.
Temple. Top 50 public school ranking. Philadelphia metro TV market. The program is down for some of the same reasons Georgia Tech has been down. We share some history. Temple has the potential to be a very successful program. Excellent regional competition and rivalries.
There are others. I don't have the time to do exhaustive analysis of them all but to be sure there are options that are regional and will add to the appeal and ultimately income of the conference in time.