The astral projection is fine and it makes sense because it involves concentration, maybe telepathy as well, but a little disappointing giving that was Luke's final moment and people expected more from him. I'm not sure what he could have done that was more impressive, but certainly not a saber fight. I never liked Yoda and Palpatine fighting with sabers. If anything an Astral battle a la Dr. Strange or a telepathic battle like Xavier vs Apocalypse would be more fitting for masters like Yoda and Palpatine.
As far as "new" Jedi abilities, it's difficult to say what would be acceptable giving that the previous films have been very consistent and we have seen the most knowledgeable and capable force users already...the biggest masters, Yoda and Palpatine, so anything that deviates too much from the core force abilities can come across as strange or out of place. Yoda and Palpatine are the most experienced and strongest force users in the movie canon, yet their abilities have limits. Imagine if all of a sudden Rey can freeze things or have x ray vision?
Sure, you could say, well the force can make it possible, but then the force just becomes magic like Harry Potter or Dr Strange, without any real boundaries. I don't want the Jedi and Sith to become Green Lanterns, capable of doing anything they can imagine because the plot demands it.
I wouldn't mind seeing energy projection like in Dragon Ball Z. And I don't mean force lightning, I mean energy blasts with their hands. It would makes sense, in DBZ they have the KI which is a life force in all living things, inspired by real martial arts teachings like Tai chi , but basically it's similar to what the force is in SW.
