Hold on to your light saber!
It's late and I'm thinking weird things again....I was thinking about how Mace Windu was repelling the electric attacks from Sid in ROTS. Well, Luke gives up his light saber in defiance before Sid starts zapping him. What if Luke had his saber and repelled and defeated Sid like Mace almost did?
Would Vader have joined in and tried to help Sid (even though Vader was handless and saberless at this point, he could still tackle or kick or do something) and let Sid finish the fry-job? Or,
If Luke won, what would he have done with his ol' pop? Kill him to bring balance? What else could he do? It would be either that or stay and get blown up I suppose?