Interesting theories. I agree with the general premise that the way Rey approaches the dark and the light can be unique. Though he's not in charge anymore George Lucas has said that the Force is not Yin and Yang, and that the mere presence of a Sith or other Dark Side Force-User is the product of imbalance. I would like for this to remain true though it's too easy of a way out and I don't think Star Wars should become a story of grey vs grey morality. The idea of a balance within one self is interesting. Perhaps the flaw of the Jedi is they never truly taught people to face their own darkness and learn to actively manage it, only to suppress it or "turn away" from it as you said. This suppression would inevitably mean some people would give in to the Dark Side.
If you're interested in my analysis please check out:
https://steemit.com/starwars/@g-com/on-failure-and-the-last-jedi
Yes yes yes! This is exactly what I’m talking about!!! Going to check out your post now!