And I’m surprised at how much I’m into the “illusion Palpatine” idea but am not convinced at all that it can be successfully pulled off in an edit.
I wouldn’t count it out, after all the ability on these forums keeps going up and I’d say there only need to be a half dozen effects shots to make it work:
-Stone box on Mustafar being disguised as a boulder
-Wayfinder in Death Star disguised as a pillar
-Tendril-like life drain from Sith Cultists to Palpatine
-Image of crystal revealed to Rey beneath Palpatine’s illusion
-Breaking of crystal with lightning
-Crystal fragments strewn across the floor
And maybe some new dialogue from Palps to Pryde
Another reason I like the idea is that it concludes the meta commentary on the fan base that TFA consciously or unconsciously began in 2015. Now the presence of Palpatine and Rey Palpatine can merely be a comment on the desires arising from some corners of the fanbase without actually forcing them into the story where they don’t belong.
I know many people are eager to remove Rey Palpatine, but I fear that in so doing they remove a lot of what I will call ‘wtf factor’ that makes the ST fun as an experiment in shlock (this is the only way I enjoyed TROS). In the end the film will feel lighter and less interesting for never even countenancing this bad idea. But with Fake Sheev the film can have its cake and eat it too.
JEDIT: The connection between the wayfinders and the Sith Crystal could be indicated through sound design. Have a similar distinctive hum or resonance whenever Rey or Kylo is in their presence, and continue this same sound when they confront Palps. It might just be in the background through most of the fight, but after the Jedi aid her Rey’s senses could be augmented enough to hear this sound and identify its source. Have Luke’s voice saying “Breathe. Just breathe. Now reach out…what do you see?”