I feel that if you have a defensive oriented head coach the one year you hit on an OC he is going to leave and then you are stuck finding replacements year after year. We have had new OCs pretty much every year with Schiano and Flood. Maybe this changes with a bigger budget down the road. Patterson and Stoops have given free reign to their OC hires and those OCs are probably HC candidates after one good year. Florida just had to pivot from a DC hire, Texas might have to soon, Chizik won a NC and was fired to be replaced by his former OC. Randy Shannon, Mike Stoops are other recent examples. I would love for Rutgers to have Arandas defense but I would rather establish an offensive identity first. I don't know what's the better route. A current HC with OC background may just be personal preference after watching us run the ball into the line for the last 10+ years.
They can leave no doubt but since coaches running the spread are ubiquitous these days it's likely easier to replace them than a good DC who I don't know know are so ubiquitous.
Let's see Bob Stoops who has had to replace a ton of coordinators. Mike Leach, Mark Mangino, Chuck Long, Kevin Wilson, Josh Heupel, Lincoln Riley. 4 of those guys went on to be HCs and Heupel was let go because of lack of production but look at Stoops' career at OU, it's been pretty good right on through.
Gary Patterson. I don't know all his coordinators but he had Justin Fuente who did well, had a hiccup for a couple years replaced those co OCs with Dough Meacham/Sonny Cumbie and is on a roll again.
I think Jim Mora Jr has had Noel Mazzone since his start at UCLA. Todd Graham same at ASU with Mike Norvell, I think he's been with him since his Tulsa days. He had Gus Malzahn at Tulsa IIRC. Tommy Tuberville had Neal Brown at Texas Tech and now Eddie Gran at Cincy both were with him through his tenures at both spots. Dabo had Chad Morris and now he replaced them with a couple guys on staff in Tony Elliott and Jeff Scott. They've done well still but you know what's really had them take off lately is the strong defense Venables has been able to create over his time there. Will that be as easily replaced if Venables ever leaves? Kevin Steele was let go after that WVU debacle and he got Venables but I'm sure that close to 1m budget helped.
Justin Fuente lost a good DC in Barry Odom to MIzzou and there's been a huge drop off this year. I don't know how many DCs Kevin Wilson has had at IU or Kliff Kingsbury at TT. Holgorsen has had a couple at WVU IIRC. These are good offensive coaches and there are others but they have hard time delivering on that mediocre defense that I want. So just like the defensive guys you mention have trouble so do the offensive guys. The thing is some of those defensive guys you mention were ones who tried to run the prostyle as opposed to spread or didn't know how to switch. Strong did before he switched to a spread, Chizik switched his offense after Malzahn/Newton left to a pro style IIRC and I'm pretty sure Shannon/Muschamp ran a pro style as well. So some of those guys seemed a little unsure about deciding on what to run or how to execute a switch over.
Now this isn't to say I don't want an offensive coach. I'm perfectly fine with it and Doug Meacham is right along side Aranda at the top of my list. It's just that I won't rule out anyone by painting broad strokes. You'll notice the offensive coaches I like are the ones who I think will pay some attention to defense and not just neglect it like others do. Meacham working alongside Patterson gives me the impression that he would like Fuente did at Memphis. Babers changed DCs after his first horrendous year on D at BG, it's slightly improved this year but still not great. At least he recognized it and he tried. Still a little wary about Babers with defense. Conversely, if it's a defensive coach I look for a guy that I think will be able to pick a good OC having had experience working with a spread in his career. That's why I liked Venables before finding out about his temper issues. Aranda is similar before his time at Wisconsin.
Point is I don't narrow the scope of who I think might be good by painting with broad strokes and instead look at things on a case by case basis.