Might be neat if evil vampire Rey had the Sith eyes.
Edit: Something like this mockup; or maybe subtler. Or even more vampiric.
Then again, making vision Rey even more obviously evil just sort of reinforces the general idea that Rey isn’t actually tempted towards the dark side at all. It’d have been more compelling, in my opinion, if there was something in that “cave” that actually appealed to her in some way. Alas.
Edit 2:
EBSynth test. Unfortunately it squishes the pupils around so I’d have to do those manually, I think. Still, plausible if desired.
That test footage is so incredibly unnerving and I think it’s great.