Brian Flores Is the only Defensive HC that should be considered by the Saints. The Vikings are not going to keep him past this yr.

Neither was John Harbaugh. There are many different ways to skin the cat.

Lots of guys that have been NFL or major college OCs or DCs have failed. There is no one size fits all solution.

You vet out the best guy for your team through the interviews, not just the black and white past job titles, especially when talking about a coach that’s been in the league this long and also seems to always get instantly promoted to Assistant HC/Associate HC at his stops and players seem to look at as a HC type figure.
Like I've said , I do like Rizzi. It's just there is nothing to go on to tell if he knows the offensive or defensive side of the ball well enough to be an NFL HC, at least with a successful OC or DC you know that they know 1 of the 2 most important aspects of football.
Since way more HCs fail than are successful and almost all have been DCs or OCs then logic says that most of the ones that fail would have been OCs or DCs, in fact I'd say that about 90% are

John Harbaugh is an anomaly, one of a kind. Most of his experience is in ST, but not ALL.
You know as well as I do that Ast. HC title is used to hire away a coach to the same position to get around the lateral move thing the NFL has. And also to keep a coach from taking the same position with another team.

The last 7 games will tell if Rizzi is a serious HC candidate because it's his only real experience at this level other than ST.
As of right now for me Rizzi's biggest draw other than he is a firey guy is that face that he'd almost for sure keep Kubiak.
I'm just not ready to put my hopes in hiring a guy hoping for a 1 of a kind anomaly like Harbaugh