Not sure how this even impacts duel. Players can already go to the enemy spawn by walking around the rafters on the map for a while and even if this exploit existed which it no longer does, nobody can get a teleporter up without it being killed and even if they did, you can walk to the enemies spawn to shoot at them literally within 5 seconds from your own spawn. AND EVEN IN SPITE OF THAT, building a teleporter into your own spawn for enemy spies is already against the rules.