Yeah, I am wondering about the limits of range, package weight, recharging operations and more for this kind of use. There are probably many headaches involved in implementing such projects.
For instance, shipping medications in baggies (pouches), where the script label is printed directly on the baggie.
Boxes within boxes, plus all the packing material, drives me nuts.
None of this is addressed though.
If this means I can have something delivered in 45 minutes, or maybe 20 minutes!, they can charge a premium for that. Otherwise I wait for the big truck to bring it by within 2 days and it's free. Right now there is no solution at any cost, in my market, by which I can order almost any product from Amazon and have it within a few hours.
In most places, the fancy technology has zero advantage over employing a handful of couriers. Exceptions would include extreme geography or traffic conditions.