CWBorne said:

I'm curious if one could split the difference between the original concept of Father Skywalker and the ESB twist and reveal that Vader did kill Luke's father... but only after the Skywalker himself was seduced to the dark side and tried to destroy Vader via a trap to prove his own loyalty to Palpatine. Darth wins and feeling the power of the dark side, turns and becomes the Emperor's new apprentice. Thus Kenobi inverted the truth; Darth only killed Luke's father when the latter betrayed him.

Of course there's also the alternate story point of Kenobi killing Luke's father which is what most people (other than Lucas, Kasdan, Kershner, Hamill, and James Earl Jones) thought because that's what was filmed on set.

Your first point of "splitting the difference" is pretty interesting really. However, Obi-Wan wasn't ever intended to be the murderer of "Tan"/Anakin Skywalker...but nonetheless the ESB twist forever made his backstory recollections to Luke complete and utter "lies"...