"Actually, there is a place where he would fit extremely well. After Alderaan is destroyed, Obi-Wan feels the disturbance, and sets down. A scene could be added directly before (or directly after) this moment, where Dagobah is once again established, and Yoda senses the destruction just as Obi-Wan does."

No, that wouldn't work. It just would not work. The pacing would be screwed - and everytime they add something they ruin the pacing, so things'd only be worse in the end.

It's like adding a scene of people on Alderaan seeing the Death Star coming up and freaking out and then getting roasted... by gosh it'd be cool to see if done right, but it really doesn't fit in the flow of the movie.