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Now comes the interesting part. The gym symbol is also on the game logos, similar to the Mega Evolution, Primal Reversion, Z-Crystal and Necrozma's brain in the previous games. This could indicate that there's more to it than just reworked gyms.
What if there were items to give pokémon the "gym boost" even outside gym battles? Like a set of armor to increase their defense stats, or magical blades to increase their attack stats, etc. That way every pokémon could use them, similar to Z-moves. But, just like Z-moves, some pokémon could have their own, exclusive items, which could not only give them "gym boosts" but also change their forms, like Mega Evolution.
And that's where the rumored "armor evolutions" could come in. Some pokémon might have in-battle "defense forms", others "attack forms" like Aegislash and Deoxys. Forms that could be used in any battle format, but probably with restrictions like one per team.
What do you think?