I guess they could make it so it's only client-side, meaning only for the local player, and all others would still see the helmet.
I don't really understand the want for something like this, though, and I don't think I want it explained to me.
Also, tears, beggars don't go into battle. Every peasant can find some cloth to wrap around his head. And heros don't exist in battles. They are created by bards.