Join the AAC or a new conference based on it. Here is what is possible using
http://www.usatoday.com/sports/ncaaf/sagarin/15 Western Michigan
21 Temple
25 Houston
27 South Florida
31 BYU
32 Tulsa
34 Boise State
38 Western Kentucky
40 Memphis
47 Toledo
49 Navy
50 Appalachian State
52 Colorado State
57 San Diego State
58 Air Force
59 Central Florida(UCF)
69 Wyoming
72 New Mexico
73 Louisiana Tech
and others +75
Take the top 12 and it would not be bad. Could it get a team into the playoffs? Probably not but it could build to it. It would have a few top 25 teams.
Other AAC teams:
88 SMU
103 Tulane
114 Cincinnati
118 East Carolina
149 Connecticut
You can't go off just the current seasons rankings. Western Michigan is #1 on the list but probably #57 or worse on the list of who you would actually want to see in your G5 conference.