I would rather that the judge finish this case before the president exercises his powers. The judge might dismiss. That would be awesome, much more so that Trump issuing pardon. The judge might sentence him to jail time or probation. That’s when the president should act.
Plus it can be counter productive for the executive to hint strongly at clemency in a politically explosive case. If the person or body returning the verdict is in a position where they will catch a lot of grief whatever the decision, you do not want them thinking along the lines of 'If I acquit I will be hated by one side for life, but if I convict there will be an immediate pardon, and the other side will have forgotten about it in a year.'
Charles I did that when the Earl of Stafford was attained. Many in the House of Lords were conflicted, but, since the King's men had made it known that he would not let Stafford die, doubtful peers voted for attainder, with the expectation that Charles would either veto the bill, or pardon Stafford, and no harm would come to him from their vote. But, by the time the bill reached Charles, the political winds had shifted, and he sent Stafford to the headsman.