Bingowings said:

I wouldn't want that or imagine it possible with the existing footage but it might be possible to add some almost subliminal images of their ghosts trying to shield Luke.

Sorry for the late response.

I don't care for this idea on a storytelling level. Force-ghost physiology aside, the pivotal idea here is that Luke is now an adult and on his own. He's lost his mentors and has to step up.

Yoda and Obi showing up to help him diminishes Luke and the dramatic purpose of the climax.