I find your last idea in particular quite interesting with the force lightning. It still leaves some room for confusion and uncertainty though, as we don't have any indication that Vader was ever Obi-Wan's apprentice, nor why he has a bitter hatred of him at the end fight. Technically speaking it would take a very talented CGI man and some actor in a costume to pull it off, but it sounds promising. I still feel that it would be nice to be able to watch the movies 1-6 and not have the Vader/Anakin surprise spoiled, but that may not be possible to pull off effectively.