AMZN can allow itself to implement infrastructure/process to use something like Al metal-air cells. Stick in, stick out, sent resulting Al oxide to re-processing. You'll get efficiency and range of at least gas engine without mess/maintenance. There are more advanced schemas available (like potassium based - more energy dense, easier for reprocessing), unfortunately most of the money is in Li based schemas which would make sense only if Li were to be the main by weight component, which isn't going to happen in any near future.
>Wide use of overhead power lines in cities makes drone delivery unsafe in cities.
that just control/sensor problem, pure tech and very solvable issue.
>I feel this is somewhat misguided
we need to utilize 3D en-mass, in particular for transportation. Whatever industry starts it doesn't really matter in big picture ... End result anyway will be an autonomous octocopter for commute :) (the autonomous cars Google develops will be great for trucks which will roam roads empty of people carrying cars)
