Scavenging the Sith blade is similar to an idea I suggested some posts back, but the issue is that the plot now rests on this blade which was created just for this film. It doesn’t feel particularly earned as a revelation.
Making that list of plot and theme issues, here are the major ones as I see it:
1: Rey needs some inner darkness, whether that be from early life experience or from an ‘evil’ bloodline.
2: Rey needs a reason to have been left on Jakku, living next to several plot-important ships/places.
3: Rey needs a reason that choosing the Skywalker family name is important to her.
4: There should be a reason that Palpatine in particular is a fitting nemesis for Rey.
5: There should be a reason why a Jedi Hunter would wish to find Rey as a child.
Considering all of these, maybe the best idea would be to return to a pseudo ‘Rey Palpatine’ backstory. The big problem with this is that it directly conflicts with the idea that Rey’s parents were ‘nobody’, and it also creates a massive plot convenience if Rey just happens to wind up on the planet where the plot of TFA begins.
Here’s a concept:
After the Civil War, the Sith cult attempts to resurrect their fallen Emperor. They have his genetic material, so they use his DNA to grow almost identical clones of the Emperor within surrogate mothers across the galaxy.
While this experiment is ongoing, the cultists manage to revive the spirit of their Emperor within the body of a rotting clone, and their revived Emperor gives the order to have these experiments destroyed, lest they grow up to threaten him.
However, Rey’s parents have come to love this child and want her to be raised far from the influence of the Sith. They discover that churches dedicated to Luke Skywalker and the Jedi are arising on planets across the galaxy, with one allegedly located on Jakku. They make it to Jakku but Palpatine’s Jedi hunter meets them there.
Rey’s parents sell Rey to Unkar Plutt in the hopes that he will take Rey to this hidden enclave, and then they face Ochi and are killed defying the will of the Emperor.
…
In this concept, the dark revelation is that Rey is not just related to Palpatine, but in a very real sense she is Palpatine, or at least a female version of him. This sidesteps the issue that we’ve already had the plot about the offspring of an evil guy choosing not to be evil. Furthermore, anyone who knows the lore concerning cloned Force sensitives will know that madness is a common fate, so this is another problem potentially confronting Rey.
Rey’s parents here remain nobodies, and since there could have been thousands or millions of surrogate mother experiments, Rey isn’t terribly special as a person either. More critically, it isn’t a huge coincidence that Rey happens to live near the Church of the Force on Jakku, since that was the destination of her parents.
Lastly, we can keep almost everything concerning the ‘Rey Palpatine’ cut in place, including the flashbacks to her parents.