could obiwan pick up the sabre from the temple? this could serve as an alternative discovery of 'darth vader's' identity? (as oppose to the holographic security footage.)

also, i was going to mention this before. have you considered changing the motive of obiwan's motives for going to mustafar? enstead of 'destroying the sith' obiwan could go to save his friend from damnation.

yoda's lines from this scene could be repaced with him talking about their exile, and obiwan could mention that he needs to do something first.