If a successor isn’t named immediately after the Odom to Purdue news is official. Then I don’t see Harper retaining any of the coordinators to be a HC. If that’s the case, let’s look at who is available:
Bill Belichick, former NFL Head Coach + plus naming his son as HC in waiting.
Dan Mullen, former Mississippi State and Florida coach
Brennan Carrol, Washington Huskies offensive coordinator.
Will Stein, Oregon Ducks offensive coordinator
Tim Banks, Tennessee Volunteers defensive coordinator
D’Anton Lynn, USC Trojans defensive coordinator
Bob Chesney - James Madison HC
Tony White - Nebraska DC