Cincinnati isn’t doing anything that isn’t already contracted out. They are getting the G5 money already allocated to the G5. It makes no difference whatsoever where they are ranked, it’s still the same slot and the same money.
And while the committee has a primary charge to prop up the P5, even if crazy upsets happen forcing them to slide Cincinnati into the top 4, that’s not a huge deal. It’s still the same G5 money (unless they win and nobody believes they would), the CFP gets a good Cinderella story, and the committee gets to claim everybody really does have a chance (even if that isn’t really true).
There is no guaranteed spot or money for BYU. BYU would be taking both a spot and money from the P5 if the committee gives them an NY6 invite. They are actively discussing now how they can downgrade this game with CC, you can bet on that.