One thing to consider about college coaching v the NFL, the work load. I remember Spurrier openly talking about his golf taking a hit because of the additional time the NFL required and the longer season.
Once these HC's like Saban, Swinney, Smart and Riley get the set up, it runs itself. Unless a highly successful college HC just has the itch and has to scratch it, he will not be happy as NFL coach but there is that pecking order where the NFL coaches feel they are better than the college ones.
Using Johnson as an example isn't really applicable. He didn't have the cap to deal with and that Walker trade was the catalyst for the turnaround. Riley or Meyer would be going into virgin territory for them, the tail wagging the dog and injuries making victims out of coaches too. And is Riley really a quality HC or just an OC?
However, if Booger wants a HC that will love his players as much as he does, hire Tom Herman, he kisses his players.
For my money, and none of it is in this, I would not look for a name to sell, I would look at what coaches like Gary Patterson, Mike Gundy and Matt Ruhle have done. They do that with fewer 4 and 5 star recruits than the Riley's and Meyer's.
It isn't about the HC as much as it's about the coordinators and position coaches he can bring. Jimmy brought a couple of good ones in Turner and Wannstedt but then again, that was a different time. And we don't know how many or which of these coaches Booger will want to retain or how much control any HC he will hire will have over that.