Here's a possible historic comp for him...despite being - in that case - the extremely successful defensive coordinator for the Ravens teams in the late 90s and early 00s, Marvin Lewis couldn't get a head coaching job, even interviews were hard to come by. He had to leave the Ravens and came to DC and was the defensive coordinator for one year for Washington in 2002 and then finally got the head coaching offer from the Bengals beginning in 2003.
I wonder if Bienemy has had to try something similar and if it goes well in DC next year that he still leaves if a head coaching offer comes his way finally. Just a random thought.