Single post in Permanent Xerneas

In movie lore even the argument of "Battle Mode" is disproven as Xerneas goes into active mode to grant Diancie it's Fairy Aura https://bulbapedia.bulbagarden.net/wiki/Xerneas_(M17). I list this as an additional reason for consideration that hasn't been mentioned before and also a point of thought of how it could be implemented without fighting. Additionally it's Pokedex entry from Y: "When the horns on its head shine in seven different colors, it is said to be sharing everlasting life." Source: https://bulbapedia.bulbagarden.net/wiki/Xerneas_(Pok%C3%A9mon) So there are multiple instances of it being active outside of combat and multiple ways of implementing that in a creative way. The only thing one would have to consider that Xerneas is inactive most of the time. But then again that rule doesn't apply to PFQ anymore thanks to the way Mega-Pokemon are handled. One way of implementation would be - that it, when it's in your party and a different Pokemon in said party changes it's appearence (egg hatching, evolution, forme change, mega evolution [...]) - it enters active mode for a limited time. But as it is right now I can understand people that are unsatisfied with the given reasonings as to why it's not part of the side and see no satisfieing and convincing reason as to why it should be this way.