Playing off hypothetical:
B1G - Oregon, Washington, Colorado, Nebraska - Stanford, Notre Dame, USC, UCLA - Iowa, Minnesota, Illinois, Wisconsin - Ohio State, Michigan, Michigan State, Penn State - Indiana, Purdue, Northwestern, Rutgers - Maryland, Virginia, UNC, Duke
SEC - Florida, FSU, Miami, Virginia Tech - Georgia, Clemson, South Carolina, Kentucky - Auburn, Alabama, Tennessee, Vanderbilt - LSU, Missouri, Ole Miss, Miss State - Arkansas, Texas, Texas A&M, Oklahoma
That leaves 21 of the current P5 teams out (WSU, OSU, Cal, ASU, Zona, Utah, Iowa St, Kansas, Kansas St, Oklahoma St, Texas Tech, Baylor, TCU, WVU, Georgia Tech, NC State, Wake, Louisville, Pitt, Boston College, Syracuse)
If you add 15 teams from G5 you have enough to make three 12 team conferences (Cincy, UCF, BYU, Houston, Memphis, SMU, Tulane, ECU, USF, Charlotte, UAB, Boise St, SDSU, Fresno, UNLV)
XII: Iowa St, Kansas, Kansas St, WVU, Oklahoma St, Texas Tech, Baylor, TCU, Houston, BYU, Cincy, UCF
PAC: WSU, OSU, Cal, ASU, Zona, Utah, Boise St, SDSU, Fresno, UNLV, SMU, Memphis
ACC: Georgia Tech, NC State, Wake, Louisville, Pitt, Boston College, Syracuse, USF, ECU, Charlotte, Tulane, UAB