After these recent FBI revelations about the plan to take out Trump with Fusion gps, Ohr., Szork (spelling), McCabe, maybe even Comey and others are witnesses. If the defense team states that part of the defense is to show there was collusion to set Trump up... not only are the above named people witnesses but so are all the people who may have spoken with them about the case. So just about every person on Mueller's team is a potential witness. A defense lawyer would then argue that a potential witness can not be a prosecutor. It would be far too prejudicial. This is a very legitimate argument. I know for a fact that argument works in California State civil court. The court ruled the lawyer could not put the case on in front of a jury but that she could remain the trial attorney if both sides agreed to a bench trial. Even if the trial court were to rule against the defense team with respect to some or all of the witnesses, that ruling would crate appellate work for years. Mueller and his team should replace themselves with people who have never dealt with the people at the FBI or the DOJ.
by the way I don't care if they prosecute Trump for a real offense. I just think it should be done ethically and properly.