I think we'd be better off if they impeach and remove Rosenstein as soon as possible. Then Trump or Sessions could appoint a replacement, who could then look at Mueller's letter of appointment, decide it's to vague, and re-scope the investigation to only look at Russian collusion. "Ooops, there isn't any? Then I guess you're done!" This takes the chance of an October surprise off the table (at least from this direction).