To be honest, I have no desire to bring in WKU... Like Marshall they are not a fit with much of the league culturally (southern team), they are not in a major media market (do not say they bring Nashville because OU is not considered to be in the Columbus market and they are about the same distance in relation to WKU-Nash) and while their sports have improved drastically over the last decade, their academics leave a lot to be desired. I think the MAC could do better going East with UMass, Temple, Army, or Delaware. I know the likelihood of getting Army or Temple is not great at the moment, but I would much rather hold out for one of those schools than settle for WKU. I really do not think they bring much to the league other than another mouth to feed. Might as well just stay at 12 unless a team that can help move the needle via television (big market - Temple or great following - Army), or a state flagship like UMass or Delaware come calling.
Zero. The odds of getting Army are zero. Not slim, not a long shot, but literally zero
Temps and UMass have already been and gone, so they won't be coming back. Neither really added anything to the MAC; we knew that Temps was merely biding its time for a better offer (which it got but has failed miserably as a contender, much like its stint in the Big East) and UMass won't be full-time MAC. Delaware, while having a perennially decent program, probably doesn't have sex appeal for the average fan.
I think what eventually will happen with the MAC is to pick up a couple 1AA schools that want to transition up (like what's happened with many current MAC teams). Maybe EKU (which is sort of an outlier in the ASUN) or a couple MVC teams.
I live less than 3 miles from U.Delaware's stadium, I'd love for them to join the MAC. That said, I'm not going to claim that I'm well connected to the program, but I don't think they have any interest in transitioning to FBS. Intellectually I know that they must have had home games this past year, but I never once knew when they were taking place based on traffic or on-campus activity. (Which, to be fair, is an argument that they'd fit in perfectly in the MAC)
Also, they're not close to anyone in the MAC. 7-hour drive to Athens, about the same to Buffalo and Ken-kron, and further to the rest. Football and basketball you could fly into Philadelphia or New Castle, but that's a long bus ride for the field hockey, baseball, et al.