Yeah, I think the choice of the next DC is critical to keep Jaire engaged. He is going nowhere (maybe the IR) next year due to his contract. But if you bring in a strong leader with an attacking D (hellooooo JL), I think Jaire will be all in.
Zimmer came to mind also and could be interesting, but I would be concerned about him relating to the younger players now days.
With a 4-3 D, I think we'd have issues with our OLBs and DL matches. Clark and Wyatt would be fine in a 4-3 (maybe preferable for Wyatt). Brooks too. Not sure Slaton or Wooden fit well. Then you have Gary, Ness, and Smith that might fit as a 4-3 DL, but couldn't really flex to be a 4-3 OLB. It can be done, but I think we have good talent for the 3-4 and shouldn't change it now. Plus, I still think the 3-4 fits better against the pass overall.