Out of those 4, #1 NEEDS to happen to create equality in their ultimate. Kylo being able to chain ultimates invalidates rey and her damage immunity. Because it only reduces damage to -1 kylo can still rebuild his ultimate bar while in his ultimate to chain ultimates and devastate rey.
The 2 changes that NEED to happen are make light side allies immune to critical hits while in ultimate stance, and some type of increase to her PvE viability to allow her to also solo HSTR. Since kylo was given a massive boost to PvP viability, Rey should get an increase to PvE viability.