Folks,
There was some fascinating stuff in a recent AW&ST, the results of a US Gov. sponsored competition, think hybrids, just like some present cars, and think a whole new approach to a swivel wing distributed thrust VTOL --- part of a big increase in efficiency was use of AC, instead of DC power, and thrust varied by prop pitch change at constant rpm. .
I would not be too quick "lay down the law" about what's possible and what's not.
Boeing and a partner are seriously looking at a Regional airline size hybrid.
Part of the design is to swap out batteries during a <30 minute transit.
As I said, fascinating.
There is an old engineering adage: "We do the improbable immediately, the impossible takes a little time".
Tootle pip!!