You would have more than eight teams. Only the final eight would play in the big four bowls.
Example:
32 teams would start the playoffs
Round 1: The first 16 games would go to the lower bowls like Liberty, Music City, etc
Round 2: The next 8 games go to the next tier of bowls like Capital One, Gator, Peach etc
Round 3: The next four games go to the lower 4 Elite bowls(Orange, Sugar, Rose, Fiesta) by order. The bowl that hosted the previous championship game would drop to fourth, with the runner up moving to host the NC. The 3rd and 4th bowl would each host two of the 4 games.
Semi: This would go to the bowl that would host the NC in the next year
Final: The Elite bowl that is in current rotation to host NC game
Not really hard to understand and doesnt extend the season no longer than the bowls already do.
Pretty simple if you have organizational skills