Also, you say that Rey hasn’t earned her position as hero in the story, but I don’t see how her being Luke’s daughter would change that.

You could change Kylo’s hangar dialogue to say, “Your Luke’s daughter”. But then when Rey goes to see Luke, you would have engineer a believable conversation between them. Maybe you could repurpose lines? Redub? Others have tried that to poor effect. Maybe Luke didn’t know until after he became one with the Force, and the mother ran away with their daughter after having a vision that their daughter would die at the end of her training.

You could recontextualize Leia’s saber as her mother’s saber, the the training flashback could be Luke and her mom rather than Leia.

I’m sure someone could figure something out, but I don’t think many people are clamoring for it. It definitely seems like the consensus is on Rey Nobody being the strongest option. It would be cool to see someone attempt it though.