Original dialogue
Vader- What is thy biding my master?
Emperor- There is a great disturbance in the force.
Vader- I have felt it.
Emperor- We have a new enemy, Luke Skywalker
Vader- Yes my master
Emperor- He could destroy us
Vader- Hes just a boy, Obi wan can no longer help him
Emperor- The force is strong with him..The son of Skywalker must not become a Jedi
Vader- If he could be turned he would become a powerful ally
Emperor- Yes..Yes he would be a great asset. Can it be done?
Vader- He will join us or die Master
New dialogue
Vader- What is thy biding my master?
Emperor- There is a great disturbance in the force.
Vader- I have felt it
Emperor- We have a new enemy, the young rebel who destroyed the Death Star. I have no doubt this boy is the offspring of Anakin Skywalker
Vader- How is that possible?
Emperor- Search your feelings Lord Vader, you will know it to be true. He could destroy us
Vader- Hes just a boy, Obi wan can no longer help him.
Emperor- The force is strong with him, the son of Skywalker must no become a Jedi.
Vader- If he could be turned he would become a powerful ally.
Emperor- Yes he would be a great asset. Can it be done?
Vader- He will join us or die Master.
The "halfway" version
Vader- What is thy biding my master?
Emperor- There is a great disturbance in the force.
Vader- I have felt it.
Emperor- We have a new enemy, the young rebel who destroyed the Death Star...the son of Skywalker.
Vader- Yes my master
Emperor- He could destroy us
Vader- He's just a boy, Obi wan can no longer help him.
Emperor- The force is strong with him. Skywalker must not become a Jedi.
Vader- If he could be turned he would become a powerful ally.
Emperor- Yes..Yes he would be a great asset. Can it be done?
Vader- He will join us or die Master.
It's not the original word for word, but it solves the "Young/Luke" dialogue change problem. Aside from the obvious removal of the extra added dialogue, the only other change is moving "the son of" to a different point in the conversation. Much less work than trying to manufacture a word that doesn't exist.