One weird idea that would maybe work in a big city setting only, for what your are describing, (which I would love to build/see exist one day) is a "warehouse o

One weird idea that would maybe work in a big city setting only, for what your are describing, (which I would love to build/see exist one day) is a "warehouse on wheels": Throughout the city you have a fleet of UPS style trucks that contain inventory. The inventory is distributed throught the trucks so that they contain a good ratio of "hot" items and "long tail" items. Then when somebody orders something, the right truck is sent on location to deliver the product. When idle, the trucks go reload on inventory in the different local shops or wait at a charging station.