The thing is, Rey has never wanted power, which is the issue with this entire ending. There’s nothing that Palpatine can give her that she genuinely wants, other than a sense of belonging and family, so with the revelation about him as her grandfather, she has just as much reason to want him alive as she does to kill him.
Rey doesn’t want power, she doesn’t want to rule the galaxy.
She wants to be a Jedi and gain a family, so unless Palpatine’s plan can give her that he has no angle.
So hang on a sec, here’s an idea: What if Palpatine reveals the reason that Rey can’t connect with the Jedi of the past is because he personally is blocking that connection?
“Do you know why the Jedi reject you? Because of me.”
“Kill me, and the spirit of the Jedi shall pass into you.”
We know he’s lying about that of course, but at least he’s offering her something she would genuinely want. And when she is finally able to call the Jedi to her in her final moment, it is the culmination of Rey rejecting Palpatine’s lie.