I would have made Luke Skywalker's real name (insert a first name here) Vader instead of making Darth Vader's real name Anakin Skywalker. This way Obi-Wan really did have a pupil named Darth Vader who turned to the dark side, joined the Empire, and betrayed and murdered the Jedi. This means that Imperial propaganda doesn't have to explain where Vader came from and Vader's "my old master" dialogue with Tarkin doesn't hint at Tarkin knowing anything. Instead of Luke not knowing about Anakin because of Tatooine being isolated, Luke doesn't know about Anakin because "Anakin" never existed.