If I was in charge of improving the playoff and bowl system under the current conference alignments, here is what I would do:
The ACC, Big 12, Big 10, Pac-12, & SEC can select their conference champion in whatever way they choose and those 5 teams make the playoffs. Then an aggregation of polls/rankings is used and the 3 best teams that did not win one of those five conferences are also added. The college football selection committee would then seed those 8 teams (I would have a rule that teams from the same conference can't play each other in the quarterfinals and if there is a team from outside the five automatic conferences they can be seeded no lower than 6).
Those 8 teams play in four traditional bowl games on December 26th. Then a week later on January 2nd in two traditional bowl games you have the semifinals. Then at least a week later on whatever date falls on Saturday you have a designated National Championship Game.
I then would limit the number of additional bowl games to 25. 5 of them would take place on January 1st and the teams would be the 10 best teams that didn't make the playoffs as selected by the aggregation of polls/rankings and the match-ups would be set by the college football selection committee (with the only rule being no conference rematches). The additional 20 bowl games would take place between December 20th and December 31st. The selection committee would pick these teams and match-ups. The rules would be that conference champions from all the other conferences must be selected, no conference can have more than 50% of its teams in bowl games (including the playoffs), and a team must be at least 6-6 in the regular season to be selected.