I would have loved to have seen the Whills, they are the deepest lore dive the series ever would have taken. As far as their ethereal nature I can only really think of themes and visuals (the quantum reality mirrored against space) over plotlines, but I like your idea that they might be discovered and considered a source of cosmic ring like power over the universe. I’m not sure how much further they should really be characterized or explained without diminishing their larger than life ever presence, should be about as ambiguous as the power of the ark in Raiders.

Honestly I think they would have to be the major plotline still to even communicate how important they are to the saga, it’s a consciousness commentary, I don’t think Star Wars has ever been as sophisticated and it’s extremely difficult to imagine how it would be integrated.

To leapfrog a bit off of what Sheev tells Anakin about the power to influence midichlorians I think this would be a great payoff to be fully realized, a Sith creation as some manipulation of dark matter. I also think invoking and involving the universe itself as representation of the Whills could become pretty cataclysmic and satisfyingly epic for a conclusion, both fated yet still down to individual choice. Multiply the hyperspace ram by a factor of an exploding star as the protagonist becomes more or less enlightened by the force and transcends as the literal “light” manifests and the universe and the individual operate as one (Neo-ish, if you like).