Sorry for the double post but I have another unrelated idea that might be more feasible.

Basically, given that we see in the crawl that Kylo is on Mustafar chasing whispers of a hidden power and we see Vader’s castle, what if as soon as Kylo finishes killing the cultists he hears the voice of Vader guiding him towards the Wayfinder and that’s what makes him turn his head so suddenly? A line like “You are ready”. And then when he reaches the Wayfinder, instead of having the voice of Palpatine say “Find me” we hear Vader saying something like “You must finish what I started”.

I think this way the audience can make a stronger relation between Vader, his castle, the Wayfinder and it quickly reintroduces Kylo Ren’s existence in the shadow of his grandfather. By doing this, when he arrives on Exegol, the reveal of “I have been every voice you have ever heard inside your head” feels even more surprising given that its giving you a twist on the earlier assumption that Vader was talking to him and also when Palpy says “Become what your grandfather could not” it now feels like its something that has meaning to him as a character.

EDIT: Here’s some possibilities I could come up with https://drive.google.com/drive/folders/12Jo7BzwKq4q8ylY4eQTz2lSoKaKpVslz?usp=sharing