I'll put my two cents worth into this.
I think that the host school should choose if they play on Friday night or on Saturday afternoon/evening through the quarterfinal round with field conflicts (only in certain cases) taken into account.
The semifinal round would be played on Saturday at a neutral site for 9-man and Class A teams and at the higher seed for AA and AAA. The designated home team for the neutral site games would be the same as now (higher seed or region number based on year if like seed).
Now for the Dakota Bowl. I agree with madseason that it should be on a Saturday, unless NDSU has a home game or other scheduling conflicts at the Fargodome, then it would be played on Friday. Since there are only four games, I would keep the Dakota Bowl as a one day event. The thing that I would change though is the scheduling format. I would format it kind of like Michigan's state final format with two different sessions with one session being the smallest and largest divisions with the other two being the second session. I would also move the first game back from 9:00 AM to 10:00 AM. For example:
Odd years10:00 AM: 9-Man Championship Game
1:00 PM: AAA Championship Game
4:30 PM: A Championship Game
7:30 PM: AA Championship Game
Even years10:00 AM: A Championship Game
1:00 PM: AA Championship Game
4:30 PM: 9-Man Championship Game
7:30 PM: AAA Championship Game
There is my opinion on the format of the playoffs...