To make Snoke more clearly separate from Palpatine, but serving him, you could change Palpatine’s line in TROS from “I made Snoke” to “I trained Snoke”.
Then the next line could just be “I have been every voice [Vader voice] inside your head.”

I’ve actually already done that. I left Snoke’s voice in since that moment lands much better with three voices and I don’t see any plot holes that would create. Just because Snoke and Palpy are working together doesn’t mean Palpy can’t impersonate Snoke on occasion to manipulate Kylo.

I love the idea of the destruction of Hosnian being a mass sacrifice to resurrect Palpatine. It’s so sinister and dramatic! Reminds me of when I wrote backstory to his resurrection where he drained the life force of Ewoks and Gungans.

A line could be potentially added of one of the cultists saying something to clarify that a sacrifice or ritual is being performed, without revealing who we are seeing.

Maybe it’d be good if Snoke was the one to say it. That plus the line about training him would really clarify the relationship between the two (master and apprentice).

I think Sasquatch’s idea about Rey’s father being a Sith scientist who ran away is great, but I still prefer Rey nobody, so I’m gonna have to agree with RogueLeader here.

I think something that would really help in regards to setting up Palpatine is having Vader’s helmet actually speak to Kylo, which would get paid off by the “every voice” line. I’m sure it’s been done several times over by now, just gotta dig up the best version.