The bowl games are money-making ventures and if you invite a team that then loses the majority of its prior starting roster is it fair to the bowl game? Why not require schools to commit to a roster within one week of the final game of the regular season, and then if a team can't commit to at least 90% of their final game roster, the bowls aren't obligated to select that team under any circumstances (conference ties, division champion, etc). That would certainly put a lot of pressure on schools/coaches to have that conversation early (are you staying here or leaving) and potentially giving late starts if needed to backups.
Maybe what they should do is just have a plus one game at the end of the season for all teams interested. The only ones not involved would be the teams in the playoffs. It might work like this:
You have 12 teams in the playoffs (for the life of me I don't understand why if you're going to do 12, why not 16 with every team needing to win 4 games to win the NC, but that's another discussion). You play the bunny bracket on home fields, then the final 8 (7 games) are played in the Rose, Fiesta, Cotton, Orange, Sugar, Peach, and Holiday bowls (we can still call them bowl games).
Then, every other team can play a plus one game on a home field (you can't play at home 2 years in a row). The schools (like everything else now) would be free agents to find a good game to play and could play the games the week between Christmas and New Years. For example, this season, Nebraska could arrange to play someone like Clemson, Tennessee, or even an old regional rivalry like Kansas or Kansas State. Rather than nonsense bowls in stadiums 30% full, you would have sold out stadiums for home games that the players and fans would love. You could also opt out if you have a roster who doesn't want to play or maybe you're having a coaching change.
In games like this, it wouldn't matter whether players opted out. You could craft a game against an opponent where both teams have a similar opt out profile, making it a futures game.
But no more having 2 teams go to Mobile or Boise for a bowl game that nobody really wants to be at. No more obvious mismatches like the FSU/Georgia game. Totally developmental, looking forward to next season. I think many older players who don't get to play in bowls or have to play in nonsense bowls would embrace this and the ones who don't, so be it, but I can guarantee that a game on December 28 in Lincoln or Clemson SC would be a sellout, regardless of the weather.