If we go college I'd give Curt Cignetti a try. Turned a perpetual 3 win Indiana team into a playoff team his first year, they're currently ranked in the top 10 this year with a 63-10 victory over a ranked opponent.
Sure Indiana doesnt have the talent to race with OSU yet, but its really rare to see those massive improvements from a school like Indiana. Turning THE basement dweller into a powerhouse is incredibly impressive. The main downside to him is he's really old.
His method to success seems to be talent evaluation, which might be able to translate to the NFL since the modern transfer portal is basically free agency. That and the unshakable confidence that only comes from experience.
Now I see the potential for a catastrophic failure too, but thats a given with any college coach.