If 2 schools left the AAC (lets say Cincinnati and UCF), I agree with
@whaler11 that Navy would back out and remain Independent. I also agree with the folks who are essentially saying "who gives a ?". The only reasons to have a CCG is to add another higher profile game to your conference champion's resume for higher bowl placement and for money. This conference isn't worth a 30 second infomercial that runs on CPTV at 2am. And the CCG winner won't have their bowl profile enhanced any by beating another crappy 7-8 win AAC team.
My vote would be to freeze this conference at 9 for the same reason the B12 is trying to freeze their membership at 10: protect resources. The pie is limited as it is and I don't want to share money with any other podunk garbage filler school. Split the exit fee money with the 9 members and enjoy the very small incremental jump in TV money until the deal runs out.
Seriously, it is getting to the point where non-P5 schools should just ditch conference affiliation altogether and adopt an "every school for themselves" mentality.