You might be right to rip off the band-aid and do one blanket pardon to be done and move on. Although the panel suggested would cushion the blow with a semblance of fairness, the left will have more time to overanalyze and vilify. I am guessing Trump does it the way you suggested. He appears to be less tolerant of leftwing critics than before and definitely will not be worried about the optics for reelection.
I think Train just despises Trump. I am not so sure he will disagree so much with how he governs. He definitely believed Trump would lead the GOP into massive election losses. Now that it didn't play out that way, I am guessing he will be more reasonable than the others you mentioned.
