There is an interesting Freakonomics episode on one-hit wonders vs. hit-makers based upon
this research from Justin Berg at Stanford. The author's takeaway was that sustained hit-making was strongly related to an artist/band possessing a diverse and creative portfolio at the time of their first hit, which in turn was related to artists/bands having to toil in obscurity for a long time, do a lot of exploration, try out a bunch of new things, etc. Think about the Beatles struggling to make things work in Liverpool for years. On the flip side, artists/bands that struck early gold were often trapped by the expectation that they would just keep doing the same thing over and over again...either they were afraid to deviate from the formula that worked once, or they were discouraged from doing so by outside pressures.
I think there is wisdom here that can be applied to looking for coaches. Look at
Curt Cignetti. He spent 25 years as an NCAA position coach at 6 different programs prior to his first HC gig. He then climbed the ladder of HC positions (IUP for 6 seasons, Elon for 2, JMU for 5). Dude built up his portfolio and certainly explored many different ways to coach. By the time he got to P4, he had a deep bag of tricks to pull from.
On the flip side, look at someone like BF. He was incubated almost entirely within the same system, and because of his lineage, he was given positions that he otherwise would have had to work much harder to earn. That is not to say he was not capable of coaching OL or TE, just that if his name was Brian Smith, he would have worked hard to get into those same spots. This probably worked against his long-term success. You can think of the 2017 OSU game as his one-hit, and he kept trying to go back to the same well, instead of exploring different ways to attack teams.
So, if we had to choose between Curt Cignetti or BF as our next HC, I would probably lean toward Cignetti.
I know it is not going to happen, but Phil Parker reminds me a lot of the defensive version of Cignetti, right down to the personality. He certainly hasn't moved around as much (he has been at Iowa forever), but he has been around the block and seen lots of stuff. He is currently the same age Cignetti was when he took the Indiana job. I would not be opposed to making him a Godfather offer to shepherd the next 4-5 years after the eventual KF retirement.