Here's how I think it should be done.
There are five P5s, five G5s and the independents.
Have the G5 figure out a way to have their champions figured out by the end of the regular season. The G5 champions and top independent play each other in three games the same week as the P5 conference champions. You HAVE to win that game to advance. If you don't win conference championship, you don't advance.
Took a quick look, and the P5 teams to advance would be (this year) Oklahoma, Ohio State, Clemson, Alabama, and Washington.
The probable G5/Independents that would get in would be Notre Dame, UCF and Fresno State. (That's assuming they won their conference championship week game.)
At the start of the season, every team knows exactly what they have to do to get in the playoffs, and every team has a path. No beauty contest.
Another upside to this is that there's no reason for teams to avoid tough OOC games. If UT and Michigan want to play, it doesn't affect their conference standings.