I agree that normally BB wouldn't stand between a coach and a better HC gig, and I think we've seen him actually encourage most of these situations.
However, this one situation seems to be a lot different with the recent hiring of a few months ago. One would have to assume that they've already addressed these kinds of potential issues, and even if they didn't, it'd be a big **** move to accept the job and then leave without even coaching one regular season game.
I can see your point on some level, no doubt; but I still don't see it even being a remote possibility-- personally.