the only way i could think of is to remove the brake shoes and weld the sprocket driver to the hub itself.
there's nothing in the hub itself that will lock it up. one way turns the wheel, the other way stops it.
depending on what motor you're using, if it was right side drive you wouldn't have to change anything, but i'd still remove the brake shoes. if you heat it up enough, the spring in the brake cone could break, and that would either lock the wheel or just make it spin like a forward freewheel.