Maybe a solution for some people. A steel cage about 1.5 metres high with a hinged flap on top big enough for just about any box to be dropped through. Bottom of cage put foam rubber to avoid any risk to delicate items. A cage of this size would make it next to impossible to reach into to get the package. The front of the cage would have a door secured with a padlock. The advantage of a cage being that you could see if a delivery had been made without having to unlock the door. Think of something similar in concept to a NZ Post mailing box but with a much larger opening at the top! I think this would be easy for couriers and they would love it.
O.K the cage would look ugly but maybe a person could put some pot plants on top or something!