td - I respect your oft-displayed engineering skill, and of course agree with your general point about altitude, drag and thrust.
I simply think the "early generation" limitations may last as long as the "kite" phase of powered flight - e.g. thirty years, roughly 1903-1933. Unless there is some "Black Swan" increase in the energy density of batteries and decrease in the general density of aircraft structures. Which is certainly possible, but not guaranteed. But pull out your slide rule and persuade me - I'd love to have an ETA for, say, a 19-seat electric transport.
And I say that as someone who welcomes electric flight and expects something generally viable and functional - on a small scale - within a handful of years (e.g. the electric Islander I've heard about).