If I had to invent a new force power… hmm. I don’t know if I can come up with one that hasn’t already been at least touched on in official media. Maybe something like the ability to put your enemies to sleep? I could see that being a cool scene for a hero hopelessly outnumbered in a critical situation to reach out with the force and watch a whole platoon of stormtroopers start feeling very drowsy and struggling to stay focused and awake until they give in and all fall asleep. Has something like that been done before?
I like this. I also feel like hypnosis would be a natural extension of the mind trick power.
In response to the OP, I hate the force-projection thing. I thing it would have been better if it was a bit more limited. Like if it was instead a “force hallucination” power. Luke could have caused Kylo Ren to think Luke was there, without anyone else being able to see it, and it would have undermined Kylo’s credibility a bit as well as providing just the right amount of confusion needed for the Resistance to get a leg up.