First, I believe that the pool of evidence used by the Mueller team and their conflicts of interest are so overwhelming they can indict anyone they want, but will never get a conviction at a formal trial as almost all evidence will be thrown out.
Of course the Mueller goal is to assemble a pack of lies that get pulled together for an impeachment article, which is a political action and not governed by court rules.
This counter suit if allowed, should allow for some very interesting discovery
Mueller’s assignment is to maneuver Trump into a manufactured obstruction of justice charge.