I agree that Palpatine ‘pouring his power into Rey’ isn’t in Palpatine’s character, and is weird for the reasons you’ve enumerated here. So I’ve given it some more thought, and maybe we can use the whole ‘awakening’ angle from TFA to explain Rey’s power.
There is no hint of Rey’s power in the Force from an early age, so it could be assumed that she was chosen by the Force only when she truly needed it. Before this, she was just like any other person. Except that someone like Palpatine may have known that the Force was going to choose her and bestow in her great power, so if he knew this he would want to get to her first, and plant the seed of darkness in her. For this concept, she would need to stay on Jakku because that’s the only way she would be involved in the story and that’s how the Force eventually chooses her, so that means that Palpatine would want to keep her there on the planet until her awakening.
“I pushed you in the desert because I needed to see it…I needed you to see it…who you are. The dark side is your destiny. Rey…”
“You’re lying.”
“I’ve never lied to you. Your parents were no one. Junk traders from the outer rim.”
“Don’t!”
“They abandoned you for a reason. Don’t you know why?”
“I don’t want this!”
“It was Palpatine’s doing.”
“No!”
“He kept you on that planet.”
(Rey sees the vision of her parents and her abandonment.)
“My Love…be brave.”
“You’ll be safe here…I promise.”
“Come back! Nooo!”
“They were under duress. Forced to do the Emperor’s will.”
“Stop talking.”
“Rey…I know what happened to them.”
(Cutaway to heroes capture)
“Palpatine saw your future, Rey. So did I. A girl from nowhere, awakening to power. But you were there on Jakku because Palpatine wanted you there. And your parents played their part.”
(Rey sees her parents die.)
“She’s on Jakku; she’s gone.”
“No!”
“So that’s where you are.”
“You know why the Emperor always wanted you. I’ll come tell you.”
But the problem with that is, once again, it ruins the point of the TLJ reveal by making her parents noble martyrs, rather than “filthy junk traders who sold you for drinking money”. Sure, Rey is more of a literal “nobody” now, but at what cost?
Personally, I still think the Plagueis life-creation route is the best one to go down. It connects Rey to Palpatine in a way that doesn’t feel contrived, while at the same time completely preserving everything said in the TLJ reveal. If you don’t like the idea of Palpatine creating Anakin, you can even have Rey be a sort of “dark Chosen One”: a Sith counterpart to Anakin, created by Palpatine as his personal revenge for Vader’s betrayal.