Bingowings said:
...If the actor was replaced new dialogue could be added along these lines :
http://originaltrilogy.com/forum/topic.cfm/ESB-and-ROTJ-Wishlist/post/635729/#TopicPost635729
Yeah, I like that! Make it so that JerJerrod is nervous about the situation with the forest creatures, not about talking to Vader.
It would also make it seem as like Jerjerrod (I hate that name!) is confiding in Vader behind the Emperors back, which is interesting.