Thinking out loud here...
Say we lose to Rutgers/Illinois and Hank/Ronnie pull the trigger on letting Eichorst go. Then we will appoint an interim AD and start the search for a new AD. But the problem with that is that AD searches generally take some time. (We lucked out last time that TO was sitting around doing nothing and could take over. That won't happen again.) Then if you don't have a new AD in place in a month (which would be hard), you are having a interim AD possibly firing Riley and trying to hire a replacement.
Here are some recent AD departures in the B1G and how long it took to hire a full time replacement
Michigan - Fired Brandon 10/2014, hired Manuel 1/2016
Minnesota - Resigned/Fired Teague 8/2015, hired Coyle 5/2016
Illinois - Fired Thomas 11/2015, hired Whitman 2/2016
Outlier -> Rutgers - Fired Herman and hired Hobbs 11/2015
People aren't going to like this, but if Riley leaves this year (by his choice or UNLs) it might be best for Eichorst to still be around to make the hire. Chances are we are not going to have a new AD named by the end of November. And if that's the case, the pool of coaches wanting to come here will be shrunk as they are going to want to know who their AD is when taking the job.