Never.
The idea is that people order their products by smartphone, possibly via an app but a website would be so much easier and they'd have to register by web anyway. Once registered they order what they want, they send me their GPS location (which isn't just GPS because cellular network triangulation is involved, but it's all functionally the same) and my computer tells a loading mechanism to load the drone with the package.
Once loaded the drone is launched (catapulted off the roof of a building), now if the drone is a plane this will be outside the inner city where I can find cheap office space and a nice big roof, or with the paramotor it can be thrown off an inner city tower, as was the intent with the multicopters. The reason for the difference is landing, even a slow plane needs some distance to safely decelerate whereas a paramotor could land almost like a helicopter, making it suitable for small rooftops, although the wind would likely be an issue. Probably the best middle ground would be a tilt body craft that flies like a plane but lands vertically, it wouldn't even need to have enough power to stay in the air vertically, just enough to decelerate its descent.
Once in the air the UAV gains altitude to about 200-300m and then heads straight for the GPS waypoint and once the package is dropped it may circle for a minute or so (because the customer's phone isn't directly controlling the package) before flying home to ideally (now this is the hard bit) land on its own and be automatically recovered and recharged, ready for reuse.
The customer doesn't control the package directly because then they might steal my receivers or someone else could read the app data and steal control of the package, instead their phone either connects to my computer which then relays the instructions to the drone which then tells the package what to do. Or because I'm thinking I'll use an Android phone as the brains of my drone the customer could just call the drone (which will only accept a call from the registered number) and then they can control the package by pressing the 1 and 2 keys (tone based control).
the larger units that transport entire containers of packages and deploy smaller delivery drones
Like some kind of flying aircraft carrier? Awesome.
I could do that with a blimp of some sort although there's really no point to it and it wouldn't be able to carry much product, likewise a floating platform could save me from renting office space but there's all kinds of issues with that as well.
But hey if this really takes off (punny) maybe one day I'll be able to afford a proper UAV carrier ship and sail around the world selling sushi fresh from the sea
?