This.
Nobody really wants these trials because of the implications of a conviction of Trump. What's done to Trump can be done to any future President.
What, really, is to stop a future President from charging Joe Biden or Mike Pence with document offenses? In Joe Biden's case, all the elements of the crime are listed; he possessed documents he had no right to possess for decades, and that's not even taking into account how they were stored or his sharing of them with his autobiographer. All of the elements of a crime are present. The only reason Hur is not charging him is because he is the sitting President, and Hur has added statements to the effect of Biden's cognitive abilities that suggest that, at least in the present, he may be considered unable to stand trial if the issue were tested by the Court.
I do not wish to see Joe Biden on trial any more than I want to see Donald Trump on trial. The remedy for these issues is impeachment. I would support a Constitutional Amendment reducing to 60 the number of Senators needed to remove a President, but with a proviso that the Supreme Court rule, prior to any trial, that the allegations for impeachment meet the Constitutional Standard of "High Crimes and Misdemeanors". (A decision in that area would have precedential value for future impeachment.) Indeed, I would include appointed Cabinet Officials in this amendment. I would also include in this Amendment that the Senate must go forth with a trial if the SCOTUS impeaches, but that the rulings of the Chief Justice that presides over the trial not be able to be overridden by a vote of the Senate.
But if it's OK to put Donald Trump on trial (particularly for the Documents case), then it's necessary (in the interest of simple justice) to put Joe Biden on trial once he's out of office. The elements of the crime are set forth in Hur's report; they constitute probable cause. I would not welcome such an event, but if former Presidents can be tried for crimes after their term, how can one say of Biden that he's not fit for trial if he was fit for office?