I wonder if it would be possible (or even a good idea) to change the twist into that Rey was a clone made by Palpatine to give his soul a new body. Might be able to be accomplished by adding a few Rey bodies in the tanks with the Snoke bodies.
Keeps the same energy as her being his granddaughter without having the question of who the hell did Palpatine hook up with. Also keeps continuity that her parents were “nobody”.