I think most people would agree that something about unmasked Vader looks off, and it’s been off from 1983 to present. Whatever visual change is implemented, the audience should probably feel pity and empathy at the human who has suffered so much with the consequences of their past mistakes.

In keeping with the stated purposes of this edit, whatever is done should lend more realism to the scene, so I’d suggest having places on his head where the helmet has rubbed the skin raw, such as around the cheeks and perhaps the sides of his head. I’d imagine that just having had a long and difficult fight, he would be sweating profusely. And finally, since we see the Emperor’s electricity coursing through his skull, there should be freshly burned areas of skin on his head.