The whole idea of replacing BK to 'get over the hump' comes down to two simple risks, and you have to decide which is more easily managed:
1. Fire BK, and hope the next guy is a sure-thing as a recruiter, developer, and CEO [or playcaller if he's a true offensive/defensive specialist]. And you have to account for the fact that you're not getting Urban, Saban or Dabo...
2. Keep BK, and hope the '20 class pans out, and that the '21 class both stays together and pans out, and that OL and DL depth are well-maintained... and keep Clark Lea.
Both courses of action have many moving parts, flaws, and unanswerable questions, but one has wayyyyyy more risk and unknowns attached, IMO.
I think there is way less risk and more reliable data that says keeping BK and staying on the current trajectory is a really strong way of approaching the national title chase. whereas hiring a new guy is totally unpredictable.