Let's look at this from another angle: ... The MAC is probably the most solid mid-major conference in the country, fb/bb. Instead of looking to exit, I would be looking at teams like Iowa State and Cincinnati (a charter member of the MAC)to find a way to bring them into the league. Surely that would mean re-doing the ESPN TV deal (which is still one of the best on the books) and perhaps changing conference championship payouts from equal shares to % based on reg season titles/NCAA Appearances and so forth. Yes, that's probably a tougher negotiation overall - but for a team like Cincinnati, which missed out on the FB Playoffs last season - it (and Iowa State) might find easier and more consistent FB Playoff entree by winning the MAC. ...
The other longterm benefit - much like when Marshall joined the league - is it will force the rest of the MAC to step up or get left behind. Buffalo is already making that move. Toledo is trying. After that most MAC teams seem to focus on one main $$$ sport (NIU-FB, Akron-BB). That could change. Finally Cincy would give the MAC a 7th Ohio team which may not sit well with some and Iowa State may be step outside of the MAC's traditional footprint which may not sit well with some (but should be a plus in my mind).
But overall, I believe trying to expand 'up' is better for the MAC as a whole, and for individual teams looking for greener pastures elsewhere, over expanding out (WKY, Marshall and others), or individually leaving for another league.