Taking a break from the Death Star Duel, here’s a tangential idea for TROS in general, elaborating on my Throne of the Sith concept.
The issue with the original idea was that while it solved quite a few plot issues, there was no deeper connection tying this to Rey’s story. So how about this:
Rey’s parents were cultists living on Exegol. They pledged themselves to the Sith, and baptized their gifted daughter to the service of Palpatine. However, after their daughter learned more than she should have of the Sith’s secret power her parents escaped Exegol and fled across the galaxy to prevent her from being killed.
Rey’s parents were traveling to Tatooine to find Luke, for they only knew of his homeworld and wished to give their Force sensitive daughter to him for her protection. However, they were waylaid halfway to their destination on the desert world of Jakku and killed.
Palpatine wants the child killed because she may know the secret of the Sith’s power. All Rey knows about Exegol now is that she saw herself on the throne, which she interprets as her desire to rule as the lord of the Sith, something that Palpatine is quick to encourage, going so far as to imply that she is his granddaughter.
When Kylo confronts Rey in his quarters and in the hangar, he says that she may be a Palpatine. However, he isn’t sure that he believes it, since there is no evidence that her parents were strong in the Force. Nevertheless, he believes that she has the darkness of the Sith within her in some form, a darkness which draws her ever toward evil.
When Rey arrives on Exegol and confronts Palpatine, she is eventually defeated and must turn to the Jedi for help. They tell her that the ways of the Jedi are knowledge and defense, and she looks inward and considers why she has visions of the Sith throne. She realizes that it is literally the seat and source of their power, and this is the secret that her parents died for. She redirects Palpatine’s lightning and destroys it, and this brings down the entire edifice and destroys the Sith once and for all.
In the final scene, Rey arrives on the planet that her parents had sought all those years ago, and there she finally claims the Skywalker name.