I’ve been messing with the big reveal scene a little using dialogue from elsewhere in the movie and I’ve got this so far. It’s not really working as a cohesive whole but I think there’s a few bits here that could have promise.

I removed the actual reveal and just have Kylo poke at her insecurity re: the dark side, but Rey’s reaction and the music seem a little over-the-top for that. I did this because I intend to experiment a little with moving the lineage reveal to the previous Rey/Kylo scene but that’s probably a dead end. “Who you are… The dark side.” doesn’t really make any sense.
I removed Rey’s defiant “I do.” from the end in order to leave it a little more open-ended as to whether she’s actually tempted by Kylo’s offer to team-up to kill Palps or not.
I’ve tried to have Kylo suggest the dyad is something to do with them both being dark-siders or emotionally damaged or whatever. One of my aims with everything I’m experimenting with is to disassociate Rey’s dark-side fears from her lineage and associate them more with Kylo Ren, as I think that would better follow up TLJ and avoid rehashing ROTJ so much. I had to trim out the ‘what Palpatine doesn’t know…’ for timing though and that does become fairly important later.