So that question had been brought up in some podcasts notably Stew Mandell and Bruce Feldman. They thoroughly discussed hotels, stadium conditions, flights, national broadcasts, etc.My idea (not likely).
Top 8 teams get byes.
Teams 9-24 play at home of higher seeded team.
Down to 16 teams, play again at home of higher seeded team.
Quarterfinals, play either at home of higher seeded team or go to "bowl games"
Semifinals - play at neutral site
Finals - neutral
If FCS can have 24 teams, now sure why FBS can't do it.
A reason they said the FCS works is because they dont need to fill these big stadiums nor is there the above issues.