If we had a hall of fame QB on the roster I might be more open to the defensive thing. We don’t. Do you think Aaron Glenn is going to help us find one? Tomlin can’t find one. And won’t win another superbowl until he does.
A defensive coach can draft a QB and a defensive coach can have an OC and/or QB Coach that can develop at young QB. It's happened many times from Steve Young, to Payton Manning, to Tom Brady.
I would prefer an offensive HC and want to be a high scoring passing team again, but I really just want the best HC regardless of what side the ball he is on. And you can still have a great offense even if you have a defensive HC. In fact, smart defensive coaches realize that getting the lead early is the best way to play defense because you force them into throwing the ball and allows you to rush the passer more aggressively. Some defensive HC have conservative running offenses, but not all of them do and there is more than one way to win game regardless of if you play in a dome or not.
Also, not having a HoF QB on the roster would make it harder to be a team focused on offense.