>>21366796>but we can't even battle with XY players on ORAS the same way we could use Rotom/Giratina/Shaymin forms in DPP?All of those forms have something in common that Megas don't: they change form outside of battle. You can't use ORAS Megas against XY for the same reason you can't remove a Giratina's Griseous Orb in battle - mid-battle form changes would cause any game in which that Pokémon can't change form to crash.
Of course they could just patch XY to handle the opponent Mega Evolving anything, with the same animation and some generic text, and it would work like any other alternate form. They don't need to add new content to the game to make them compatible. To be honest I'm not sure why they didn't do it this way, other than laziness.
