I think Staley would be a better hire than Evero because nobody is going to touch Staley with a ten foot pole as head coach for a while. So hiring him you get a guy who is strong schematically in the Fangio scheme but who you don't have to worry about replacing if he kills it. And guys who get fired as HCs often kill it when they slot back to coordinator. Probably because it's so simplified in comparison they just get to work and deep dive that scheme.
But I'd be fine with Evero if McVay goes that route. One thing I don't think people realize is that McVay is very knowlegeable with that defensive side of the ball. He gets all in there to understand the rules so he can scheme against it. Everyone knows he wanted to run the Fangio system but he also wanted to know the rules by having a disciple in house so he could cook up shit to work vs it.
So whoever he hires on defense will almost surely be strong. I suspect this year though that he's going to need to promote from within. Because he has two position coaches who are killing it (Henderson and Pleasant). And Pleasant is the passing defense coordinator so he's integral to the back end that has kicked ass in spite of not too much pressure support. This means Morris takes one with him, and the other might leave too I'd expect if the DC job isn't offered.