Sasquatch, thought I’d share some ideas about what you shared.

I like the idea of using that shot from the Star Wars: Eclipse teaser to imply that Palpatine is being resurrected.

I think one idea I felt made since was that Palpatine was waiting to reveal himself until after Luke Skywalker, his greatest threat, was dead. I think the way poppa’s edit ends, where Kylo Ren hears a voice saying, “Find me.” at the end of the film helps with that idea some. But there’s never really a line that ever makes that clear, if that was the intention.

At the very least, I could see a brief glimpse of that shot thrown included in a vision in one of the ST films.

This might be a little out there, but for some reason this idea popped into my head. What if destroying the Hosnian system served two purposes? Yes, it was to paralyze the Republic, but what if it also served as huge sacrifice to resurrect Palpatine from the dead?

I could picture a new sequence in TFA, where we use that shot of the Hosnian destruction can be seen from the sky, but we see it above a few different planets. Coruscant, Naboo, etc. Finally, we cut to Exegol. We see the Hosnian cataclysm through the opening at the top of the Sith temple. We see hooded figures chanting. We hear cries of a billion voices echo through the Force. Then we see a figure rise from the black liquid (the shot could be color corrected to better match Exegol). 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 we could even have a close up of Snoke to imply he is there to witness it. Anyway, you would have to do it in a way that wouldn’t disrupt the flow of the film, and didn’t feel too disconnected. So maybe Snoke being there could help it feel connected to the rest of the film more.

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 do like the idea that maybe Palpatine’s spirit could have potentially been pulling strings, but wasn’t physically resurrected until the Sequel Trilogy. Regardless, the “I trained Snoke” line could help imply that Snoke was serving Palpatine, and maybe he trained Snoke either as a disembodied spirit, or even before Vader killed him.

One idea I’ve had for a long time is to have Kylo’s first TROS scene be him touching Vader’s mask and seeing a vision that leads him to the Wayfinder. Perhaps in this vision, Kylo could get a glimpse of Snoke on Mustafar or Exegol, to help connect him even more with the Sith Eternal.

I don’t think any explanation is necessary for who Rey’s parents were in TROS.