The films doesn’t need anything to do with Anakin or Vader, something that is so played out and over done that it’s a toy selling joke at this stage. The tragedy of Vader gimme a break.
What we do need however is a ghost or vision of some kind. I’m thinking Kylo seeing the past, and feeling regret. He dreams about his parents and his uncle. Something he buried under all the rage. And then he realises he screwed up. Get all three classic main characters in one last scene, something special. Then he can die.