I believe the current Power 5 has 64 teams (Big Ten 14; SEC 14, ACC 14, PAC Twelve 12 and Big Twelve 10). Realign and make the Big Twelve go away. The Conference Championships pair the winners of each division. This leaves four teams — but determined on the field. This grouping is for football only. The Power 5 conferences can remain as is for the other sports.
What about Notre Dame? They can join a conference (already ACC for everything but football) or just go away. If ND wants in, then dump the worst team — probably Rice.