Cliff Warren would be a great addition, but he went to Maryland to be closer to ill family, I believe. If I was going the bring back route, I'd like to see LaBarrie or Charlton Young, but I think they've advanced too far at this point, if you assume a pecking order among assistants.
This is weird timing and it will be interesting to see if Dollar & NDiaye get bumped up and we bring on a hungry recruiter type that knows other parts of the country or bolsters the effort locally *cough* Winston Neal *cough*.
Losing Coach Schmidt is definitely a loss, as it's my understanding he's the one who led the development of Daniel Miller, and the timing sucks. That said, he's seeking to be a head coach (was in the running for the Dayton job) and people springboard from Donovan's staff to be a head coach - Pelphrey, Grant, Smart, etc.
Best of luck to him.