I think that at this point, and by the treatment the PT has had, it's rather useless trying to hide Anakins identity as Vader. Radical RADICAL edit has to come through to make it believable.

Don't know what Ady (considering what he said of an hypothetical ROTS:R edit) has in mind, but suppose we just don't see Anakin's surgery... ok, we have obi wan's tale in ANH, "a young Jedi who was a pupil of mine until he turned to evil"... DONE, no more secret.

So IMO, we just have to resign this WTF moment ESB has, and try to make something more cathartic out of it; which, is indeed possible, and doesn't require as heavy edit as the idea of giving Obiwan a new apprentice, or rotoscoping Boba.