So it hit me, if I'm doing this crazy Shiny Ralts thing... I should make sure it has a good Gardevior compatible nature when it hatches.
From my experience with Gardeviors, they want damage. They're not frail, but they're no tanks either as all it takes is one good physical move to put the hurt on one. Special Defense is good, though.
So, I'm thinking Modest is a good nature. +Sp. Atk, -Atk. Was also considering Calm for +Sp. Def, -Atk, but I don't have a Calm Ralts to use. Or a Calm foreign Ditto.
Besides, Gardevior makes a decent Special Sweeper with Moonblast and Psychic,doesn't it? Calm Mind as a third and then... something TM for flavor in the last slot. Protect, Rflect, Light Screen or something that's super-effectve against Steel would probably be worth looking at.