Maybe not ‘Amazon’ - advertisement baaad
But, a ‘Shipping Center’ or something like this could be interesting. This would also give you the opportunity to add in Drones and Copters which you could control, similar to the RC cars.
The ordering of items could be nice too, however, i Would make it a bit more difficult. Don’t forget that, even when automated, some people will be in there in order to watch over the drones and/or repair them, if need be, and those will be zombies, probably bashing up all the drones and machinery.
How about some sort of ‘quest’, where you actually have to find the Shipping Center first, get in there, get rid of all the Zombies (Technicians?), and then you might need to repair a few things, like a few drones, the backup generator, maybe some machinery…
And >then< you could try and order stuff via a console, or even with a PDA or something similar.
Another problem could be that all the machines/Generator will produce a bit of sound, it might lure zombies to the location so you’d either have to put defenses up or visit every now and then in order to make sure that they don’t overrun the place.
On Another note - this shouldn’t be an endless pool of items either, especially if you follow the setup I had in mind. They can’t get new stuff in their warehouse, so eventually the center would run dry ; the only exception would be if you personally refill the warehouse, just so you don’t have to drag all your stuff with you all the time…? Not sure if that’d be useful though if you have to wait several hours just to get a few pipes and scrap metal to build something 