Although I dont like the fact that Shaw was replaced,as for me and all you guys he is the face of Anakin for the OT,it made more sense to me than some of the other changes made.The face that we see in the reveal scene is essentially the body of Vader.The face of Anakin prior to his fall is Hayden Christensen.With his redemption he is returned to his younger true self not the battered,burnt broken old man in the suit which is the last remnant of Darth Vader.
Having said that,though,there was no real need for it.