Just being a force user is enough for them to have to deal with the temptation of the dark side at some point in their lives, and it's been shown with both Luke as a young man and Anakin as a child that the Jedi think they need to be trained from a very young age to stand a better chance of avoiding temptation. Rey's a young woman who either has no training or who is trained but has no memory of it, either way that's a danger. So you have a gifted, powerful force user who's growing stronger by the minute with absolutely no knowledge of how to deal with that, who's been surving on her own after her parents or whoever abandoned her, so we have a healthy source of insecurity and uncertainty for the dark side to get its hooks in, all set up in the first film. I'm not saying this is how it's going to go because honestly, who knows? Just my thoughts.
Then there's the two things which really stood out to me during Rey and Kylo's fight. First, there's the moment where their lightsabers are locked. It could just be a neat visual effect but I'm going to give the people behind the camera the benefit of the doubt. Both characters are face to face and their lightsabers are illuminating them in the dark. We see both characters' faces flickering between red and blue, neither one sticking to one colour.
Second, the moment Rey beats Kylo. Our hero is pacing, almost snarling, while our villain is injured, afraid and in total shock on the floor. Take away the obvious white = good, black = bad costumes and take that image on its own and you'd probably think the bad guy had just won.
Edit; Bobby, I stand corrected, that would be excellent to see. I just don't think that's what they're going for with his character. He tried going maximum asshole and it didn't really pay off. I absolutely would pay to see that story though. You speak wisdom.
