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!