I have no inside knowledge on who the next Michigan Defensive Coordinator might be. I don't see Brady Hoke doing something like hiring a big name guy like former Miami head coach Randy Shannon (even though I wish he would consider it - Randy would bring instant respectability to the role and be a huge asset for recruiting Florida), I see him going with somebody he knows and a coach that is familiar with the University of Michigan.
I believe the best person to fill that role is Green Bay Packers Defensive Line coach, Mike Trgovac. Mike has been a defensive coordinator for the Carolina Panthers for 5 years and has been a defensive line coach every other place he has been to. He played for Bo at Michigan and ironically was also a DL coach for Ball State. He even has a couple of years coaching at ND.
He was born in Youngstown, Ohio which should bring some credibility on the recruiting trial in Ohio (even though he probably hasn't recruited in some time).
Having a former defensive line coach as your head coach and your DC might be a bit redundant but I still think it would be a smart hire and certainly would help Mike Martin get ready for the NFL draft next year. D-Line is also a big area of need for recruiting and skill development for the current Wolverines.
From NFL.com:
Mike Trgovac
Defensive line; born February 27, 1959, Youngstown, Ohio. Defensive lineman Michigan 1977-1980. No pro playing experience. College coach: Michigan 1984-85, Ball State 1986-88, Navy 1989, Colorado State 1990-91, Notre Dame 1992-94. Pro coach: Philadelphia Eagles 1995-98, Green Bay Packers 1999, Washington Redskins 2000-01, Carolina Panthers 2002-2008, joined Packers in 2009.