There is already talk of the Big 12 and ACC merging to keep up with the Big 10 and SEC. The ACC will have to do something following Florida State being left out of the Final 4 and threatening to leave and sue the conference. Of course, that will create a massive conference of 33 teams (16 - Big 12) & (17 - ACC) which does not appear viable. The Big 10 will have 18 members next year and the SEC will have 16 for a total of 34 teams. That is 67 P5 schools out of 134 or 50%. 11 of those 67 P5 schools will make the playoffs. 1 of the 67 G5 schools will get in. Maybe it is time for a G5 championship. A P5 and a G5 playoff system will have 24 teams competing and can use bowl games for the bracket games. Or the G5 can create a 16 team playoff model as you suggested which would be favorable.
There were 82 bowl slots this year with only 79 eligible teams, so 3 ineligible teams were added. And this is outside of the 4 teams competing for the national championship. The bowl games are becoming a joke with 6-6 minimum records and players opting out with poor attendance. While it is better to be in a bowl game than not, it is no longer a great accomplishment.
Will bowl games continue to be viable in the future with players opting out and transferring (like Florida State this year) and 6-6 minimum records making bowl games a farce? There was only 14,485 announced attendance at the N.O. Bowl. Other bowls struggled with attendance as well. I don't know what the viewership was, but these games pretty much have meaning only to fans of the participating schools. Will sponsors continue to fund those games? Having a national championship for G5 with a 12 or 16 team playoff may be the only thing meaningful going forward and a true reward for G5 schools who have no real shot at a P5 national championship.