Just a suggestion, but perhaps you could allow Arceus in, but not allow him to hold any plates and no attacks above 60 or 70 base power. Just a thought. I kinda hate that he's excluded since it's a challenge that is here to allow legendaries. XD You don't have to go through with that though, just a suggestion as I said. I might eventually join that challenge when I have a free game and available legendaries, as I don't hack.