Locking the thread for the update. Stay tuned!
I think you do neglect to realize one thing that Garde has over the CM Fairies - It's not nearly as reliant on Magnezone and overall just fits on a lot more team structures as a result. While Florges and Sylveon do function more as wincons, Garde is moreso just one of those mons that's in and out while dealing very large amounts of chip. Trick and Healing Wish (as well as a bunch of other very underexplored support options) also provide very useful support against fat that the other two Fairies can't.Gardevoir B+ --> B+
While I agree that fairies are on the rise, Garde doesn't really use the best sets well. B+ matches the strength of Scarf and Specs, but CM Fairies are the strong ones really. Even if you eliminate Fairy resists, Gardevoir doesn't give you an easy path to victory, just a decently strong offensive threat. It also can't really beat Tera'd threats unlike Florges and Sylveon which can get through Tera Steel Mence or Tera Poison Gastrodon for example. It also lacks their defensive utility.