If I were re-cutting that scene (and, let's be honest, it doesn't really need it), as Vader looks on as Luke is microwaved, I would intercut snippets from the prequels -- half-remembered pieces from Anakin's past, little pieces, nudges from Palpatine that he'd never put together before. The flashback fragments would show Vader realizing: Palpatine had set him up from the start.
He would also remember losing Padme, who (he still believes) died at his hand. Now he is confronted with losing the son he barely knew (and the daughter he never will). And so, [em]silently[/em], he turns, grabs the Emperor, and throws him down the tower shaft.