The guy Drumpf picked, Whitaker (whose appointment may not be kosher, I'm not quite sure) wrote an op-ed saying that the Mueller investigation should be terminated or starved for funds. First, that eventuality HAS to have been prepared for. Second, Whitaker should have to recuse himself (not that I think he will) because of a conflict of interest with the Mueller investigation, he chaired a campaign for one of the witnesses in the investigation, a guy named Sam Clovis.
Also, I didn't think about this, but now that Sessions is out, he could be called as a witness. Obstruction is one of the big charges facing Drumpf and now he could be called in to provide evidence, which he most likely has.