Imo if Steele isn't going to be the dc, he should be let go, because it will probably be a one year stay if not. He is a good dc, and will find that job somewhere. For continuity purposes dc or nothing.
Coleman also got significantly better under him, McNeil and Randolph were both pretty darn solid, plus TK before his injuries. We could have done far worse, plus his recruiting experience can't be overlooked.
Heupel seems to be trying to get the best he can for the defensive side. He knows you have to be able to play defense in order to win in the SEC. So let's see how he and Banks fill out the defensive staff. My guess is that he will tell Banks "I've given you the best I can get. Now you figure out how to hold our opponent under 30 points. I'll handle it from there."
This, IMO, will be UT Football under CJH. It's going to be different, for sure. Maybe we finally caught lightning in a bottle.