I understand your point, but between Tennessee and Detroit, I would have to go with Detroit. The DC thing would be quite the deterrent, which I didn't know about.
I think the choice is pretty obvious. Do you think Matt Stafford is a franchise QB? If so, you take the Detroit job and run, especially as an offensive coach like Whiz.
If you do not think that Stafford is a franchise guy, but merely a product of Calvin Johnson's success, then that job is a future firing waiting to happen, because in 2 years, maybe 3 it will become clear that Stafford is not the guy to win for them, and as a result the guys who will get canned are Stafford, the HC (especially the longer it takes to figure out Stafford isnt the guy) and possibly Calvin Johnson if they start over entirely.
Thus the Tennessee job is much better option because they have no established QB, and Whiz will basically get to pick his own, be it this year or next.