Actually, I don't see why we shouldn't ban anything that's not a Pokémon from Ubers, whether Arceus is banned or not. We're already doing it with the clauses.
We've already banned shit in Ubers (Evasion, OHKO moves, duplicate Pokemon
Teams with Arceus cannot enter battle.
In "proper" implementation, you are permitted to battle with Evasion or OHKO moves, but executing the move will result in a forfeit. That means there are (far fetched) strategic implications.
Pedantic, yes - but not a ban, just a rule. If the moves were to fail for whatever reason, you could use them!