New MAD idea: at the end Obi-wan could "die" Something like this.

Emperor: Lord Vader, we have a new enemy. Obi-wan kenobi.

Vader: Yes, master.

Emperor: Kill him.

Vader: As you wish.

Then Vader would chase Obi-wan (Tie fighter vs Jedi fighter) and Obi would be hit and we would see his fighter smoking and falling in some atmosphere (maybe Tattoine).

This would explain why Uncle Owen thinks that he died, and would keep the surprise about Ben kenobi.

Owen could be Owen Skywalker and he could really be Anakin's brother.