When Cincinnati made the 4 team playoff they would have gotten a Bye in the 12 team model. Possible, maybe even more likely then you think in the current landscape. Example. Lets pretend Boise State actually beat Oregon earlier this year and beat Wash St. Then ran the table in the Mountain West.
Say the ACC/Big 12 sort of beat up on eachother and each winner has 2 or even 3 losses. I could see Boise State being ranked higher then the ACC/Big 12 champions. I mean right now They are number 17 even with the loss to Oregon. The Big 12 campion probably ends up ranked higher then them, but what if they would have been Oregon adn the Big 12 doesn't have a 0 or 1 loss champion?