Martin is an interesting discussion as well. Hasn't had the trajectory of success like Leipold or Lewis, he's MAC coach #86 to be talked about, and there's nothing particularly distinguishing that stands out about him.
But....worth noting he coached at ND on *both* sides of the ball, was recruiting coordinator at ND for 2 years, and won two national championships at Grand Valley. Chicago area native, played LB at Milliken, and he's got a great sense of humor to boot.
For better context on his success as a coach, Miami was 4-12 in conference his first two years, and now 24-11 his last 5 years, including 2-1 this year. He may be very happy at Miami, I don't know. Wonder what his interest would be in a Big 10 job.