Please stop citing the tourney. The two are not remotely the same. You have automatic qualifiers, conference champs in this instance, and then at large teams are chosen based on a multitude of criteria. So who are your at large teams for high school football? 5 win teams? Is it based on power rankings or just wins?
The formula to get into the NCAA tourney and seeding them are relatively the same(SOS, good wins vs. bad losses, computer rankings, etc.). You're talking about two different systems to qualify for the playoffs in football and then another entirely to seed them once in the playoffs.
If you go that route teams like Provi get screwed; sorry you didn't have 5 wins so you don't get in, but if you had made it in then using our power ranking system you likely would have been a top 20 team in your class.