^Interesting thought. The other moral problem is why did the most powerful living Jedi sit in a swamp for 20 years while the galaxy burned. There wasn't anything he could do beyond Dagobah? I suppose it could have been addressed with some quick expo about Yoda making such a strong impression in the Force that he could instantly be found beyond the Force-obscuring power of the bog world, thus blowing any operation and bringing the combined might of the Emp and Vader down on him. Luke refusing to return would help with logistics, certainly. Ben would need to stay close to protect Luke. ;/