I am only at Chapter 8 in XC2 as of now and it has been months since I last played it. Personally, I have been pretty disappointed not by the story or gameplay, but how the character progression and development is done. I think that aspect falls flat compared to XC1's characters. Lately I have been getting into great anime/manga now, and it has gotten me to pay more attention to stories that are mainly character driven. Shulk was more interesting as a character than Rex IMO. As interesting as Rex and Pyra would be as playable Smash characters gameplay wise, I have less of a desire to see them in the game due personal game gripes.
(Also, I have been pretty disappointed with the fanservice. As cool as it is to see Nintendo be riskier with lewdness, the fanservice is too minimal in the story. As someone that loves fan-service in anime now, it makes me disappointed. ;_; )
But hey, I have heard that Sakurai was praising XC2 apparently back in Famitsu, and I am pretty sure Rex+Pyra has a pretty good chance regardless of my opinion.
Good luck to you supporters.