First, I don't think BYU will end up in the Big12 as there too many issues revolving around their TV contract with ESPN and being independent (read: ESPN contract). If the Big12 and BYU do resolve their differences, then they're an automatic invite. The current situation doesn't bode well for an invite to the conference.
Louisville, geographically, is a good choice. Their FB program is decent and can improve with access to TX recruiting and Big 12 TV money, plus add a major TV market to the conference.
West Virginia adds both strong FB and MBB traditions; their following is primarily eastern (PA, WV, OH, MD, VA) which can add to the conference's TV footprint. Major athletic programs well supported.
My 'Other' is Tulane. Chuck Neinas mentioned them as an expansion candidate. Good academics (AAU member), mediocre FB and occasionally decent MBB. Located in another major TV market in the south in a state rich in FB and MBB recruits. Lots of potential to rise with Big 12 TV money.
There is my three minus BYU. If the situation with BYU improves, then sub BYU for WVU.