I already toyed with mentioning them but now that you did I have to say that the current Force ghosts are a cool concept but also very problematic.
I mean Yoda already could talk with Qui-Gon in the prequels but apparently that also required a technique from the living side to do so. It's what Yoda teached Obi-Wan later. Also apparently not much came from it. It's not like Qui-Gon had some hidden insight or anything like that.
Sith ghosts also already existed but they are not something you could just talk to. They are basically the rage of the person even persisting after death and they would try to possesses you and drive you insane so staying away from them as far as possible was the best idea.
These Force ghosts from the sequels though are the exact same person they have been in life. They can appear out of free will and they can actually interact with the real world.
Again a cool concept but if you want to expand on it you will really have to clarify how all of it works because otherwise you open a huge can of worms. Like why aren't these ghosts helping in dealing with problems? How do you deal with an entity you apparently can't interact with but they can interact with you? Do they age or will they be in this state until the end of time? Could they move on if they wanted to? How do you even enter this state? Can they just appear everywhere they want and you know potentially spy on people?
Like I have nothing against building on it but this is a concept that requires a lot more thought being put into it and if they don't then I would be happy if they would rather quietly drop the whole thing.