Just the last 3 should be retconned , yes the PT could have been done way better but maybe instead of retconning them just add a movie inbetween Atoc (since atoc failed so badly) and Sith showing anakins decent into darkness better. Use clone wars arcs if you have too. Then just get rid of the ST all together, call them a mirrorverse so people can enjoy them for what they are well made movies filmed in the star wars universe but that break all continuity in character and the force itself. Then hire MH back, throw gobs of money at HF to get him back, Get AD back, even Poe and Fin, just leave rey out of it cause she wouldn't exist if the ST never happened and Palps died when he was supposed to. In order for this to happen, KK needs to step down, and JF and DF get promoted in her place.
If they decide to keep Rey then well she makes the perfect sith, raised without love or anyone to care about her, she could easily be seduced by the darkside. Having Ben be seduced when he was raised with love and compassion is a horrible message to send society. Its as if they are telling us as parents you suck, you just ruin your kids. If they had just made her evil they had the perfect opportunity to parallel the Jedi's failure with Anakin and also send an even better message. Rey much like Anakin was stripped from the family she loved at young age then raised by uncaring monk type people, or in Rey's case it was even worse she was raised by despicable people. What is the commentary here that nurture means nothing, that we can treat our children like **** and they still become good people. This is not a good message to promote in my opinion or on the flip side you can shower you kid with love and kindness but they will still end up being serial killers