I worked it out where you could have 11 Divisions consisting each of 10-12 teams, based more or less on geograhical location and traditional rivalries.
Each Division would be split into two-levels, with one team from the lower level playing in the upper-level, based on a playoff game from the previous season, so that you allow the smaller schools a chance.
Every team plays the other in their division, which avoids a situation where a team potentially avoids playing the tougher teams, which is a big problem with the current system.
So with 11 divisions, you take the 11 division winners, and put them in the Round of 16.
Then you take the 11 second place teams, and have them play each other to round out the other 5 teams.
You would have to have a play-in game between the two lowest-seeded second place teams, to get to the 5 First Round Games.
Army was fun to watch. I wonder how they would do if included in the playoff.