[verum ago]

Why can’t they just do it like the FCS does?

Funny, isn't it? There's about a zillion sports, professional and non-, for all ages, that carry out championships under various tournament structures without the degree of controversy over the systems' fundamental structures that Division I FBS sees. I mean, there're always controversies, but FBS seems like the only one where there's a perennial consensus that it's flawed on a basic level.

As you point out, if only there were some model system that could be adopted or adapted for FBS use...

[MuttTheHoople]

Bowls are such an entrenched tradition in major college football, that you can’t have a traditional playoff system like you have in FCS, Div. II and III.