I'm with you on the Vader unmasking. After seeing the back of his head in Empire and reading he'd fallen into a molten lava pit after his duel with Kenobi, I was expecting an horrific burns victim. Instead we got a kindly old man. I guess this shows that Lucas thought we could identify with someone not disfigured and more easily "forgive" them in the few minutes before the end of the flick.

From what I know, Marquand was back-seat directed by Lucas.

I don't know that Spielberg was up for Jedi ... I do know that Lucas' spat with the unions came (in part) from not crediting anyone at the start of Star Wars. The argument was that he gave himself credit "A Lucasfilm Ltd Production" but no one else until the end-crawl. Utter bunk for an audience, but for people relying on residuals and such, key to getting union rates.(?)