Bingowings said:

Drop in a line about Kenobi already having pupil before he takes on Anakin and remove the Skywalker name from the PT and you have all the cover story you need to keep the OT surprises and still tell much of the same story only better.

Except, you still have Ben describing Luke's father to him in ANH as a great pilot, an old friend etc. If we never meet anyone else who could match this description in the Prequels, and instead the closest we have is "Anakin" Christensen, then the game is up. The solution to not mention the name Skywalker only works if there's another character Ben's description could concievably pertain to. Otherwise the audience will never buy it.