Personally, I don't have a huge problem with Christenssen's insertion at the end of ROTJ (I understand your gripes, but it doesn't bother me so much). Maybe this is because when I first learned that Hayden was going to replace Shaw at the end of Jedi, I thought they meant that he was going to be aged with make up and proshethics and inserted into Vader's helmet removal/death scene, so when it was just his ghost, I was happy. The moral is it could have been much worse, so be thankful.