I love Tulsa for C-USA. Instant hoops credibility. I have always loved C-USA on paper for hoops, but some of the team slike Marquette and DePaul are perpetually overrated. Tulsa would add an awesome basketball program that can really deliver in the tourney. They'd only improve with C-USA membership. With Tulsa, Cincy, and Louisville, you guys would be as good at the top as anyone.
As far as football only members go, why not add Navy? Having both Army and Navy would really help if Congress was a factor in a dispute over the BCS. I'm kinda surprised no conference has considered making that rivalry game a conference game. If you could pair it up with your conference title game, you'd have a real winner and tons of bonus air time and exposure.
I'd still like to see Marshall added for football. Dump UAB, bring in Tulsa and Marshall. You instantly go up a notch in both sports. Your guaranteed three heavy hitter in hoops (as well as several other semi-succesful teams), and USF, Marshall, and TCU (and hopefully USM and Cincy) will continue to improve in football.
C-USA has looked into bringing Navy in the conference in the past, only to be rebuffed by Navy's athletic department. The Navy fans say they want to be in the Big east and they want Army to come along with them. Personally I hope Army stays in C-USA. Many C-USA teams have Army bases near by, so the officers can watch their alma mater more. ;)
Tulsa actually had a chance to join C-USA when it formed, but opted to join the 16 team WAC instead. I think Tulsa regrets not joining C-USA now, and if they get a second chance to join, I don't see them passing it up.
I'd love to see Marshall added also, but all-sports is the big issue with Marshall. While the MAC is somewhat weak football conference, it is a very strong basketball conference. (the midwestern equivalent of the ACC, IMO.) When C-USA looked into giving Marshall a football-only invite, Marshall scrambled to find a good conference home for its other sports. They figured that the Horizon League wasn't too bad for bball, so they tried to join that, but the Horizon League wasn't interested in Marshall bb. The MAC doesn't allow bball-only members in the conference (although it does allow fball-only members), so Marshall couldn't leave the rest of its sports in the MAC. Marshall told C-USA they'd love to join, but they wanted an all-sports invite. That's where C-USA and the Herd stand today.