The power 5 conferences really should be their own league. Also Power 4 makes more sense, with a 4 team playoff.
However, if it's easier to keep the conferences basically the same, not including imploding or expanding on their own, a 6 team playoff is preferable to 4. 1 and 2 get a bye, 3 and 6, 4 and 5, semis,championship. This allows conference champs all a fair shot, with the expectation that champ be declared Big 12, and allows for a single at large, such as a highly ranked independent.
8 would also he preferable to 4, if the top 4 seeds earned a home game, saving on travel costs,and finally forcing southern teams north.
Completely imploding what exists is simply not feasible. Either of the above scenarios keep the regular season important, and provides equitable access.