I have mixed feelings about a G5 playoff.
Why would a school like UCF or Boise St. turn down a NY6 bowl against a top 10 program on national TV to play Buffalo or UAB? The AAC has bowl affiliations with the SEC and Big 12. I just don't see them embracing the best of the rest championship when their top 3 or 4 teams have better options.
Since our road to an Access Bowl is so difficult and our bowl affiliations are so bad, it would probably be a step up for us, as well as the MAC and Sun Belt. At least, that's how it felt when we played NIU in 2014.
I think a 4 team playoff would probably make most sense until the next round of realignments and relegation, with the assumption that several of the top programs would rather opt for a NY6 or bowl against a P5.