With my previous draft, her journey would be different in that she is the one claimed by Palpatine as his own due to the fact that he “perfected” the method of creating dark life through the Force with her. So, take whatever evil predisposition Kylo has in him, and multiply that by whatever factor you deem fit.

That being said, the only way your approach works is if Kylo simply avoids talking about the Skywalker’s family origin at all - leaving it entirely up to the viewer’s interpretation whether Palpatine did the same thing with Anakin that he does with Rey. But this also removes the parallels that you mentioned, and makes the dyad forming between them less interesting in principle. There just wouldn’t be a lot to talk about in the second paragraph there.

I dunno, I’ve heard that many people didn’t like Vader being revealed as Luke’s father when ESB first came out. I think a lot of people voicing their distaste for the idea that BOTH bloodlines were created to be dark are experiencing a similar phenomenon. Once again, I’d like to make it clear that just because Palpatine’s machinations led to the creation of somebody who is dark-natured, that doesn’t mean that the Force itself can’t later choose that person after the fact to bring balance. I think that’s what makes this idea so powerful. You can take somebody that was meant to cause so much evil, and through fate have them overcome that and bring about good and balance. It’s also hilariously ironic in that Palpatine meant to create the ultimate Sith Lord twice in a row, but both times their spirit/heart overcomes their evil nature and kill him.

EDIT: Hell, the reason Palpatine created a girl the second time is probably because he’s a sexist and thinks she’d be a pushover to his will. It’s all just really funny to me how much what he intends blows up in his face (literally).