I'm much less optimistic. Even when factoring in the poor thermal efficiency of gas turbines (~30-40%) compared to electric (>90%), the usable specific energy gap remains immense. Jet-A still delivers roughly 14 times more useful work per kilogram than modern batteries. Removing fuel plumbing and tweaking airframes won't overcome that fundamental physics. Also the issue with the high-altitude efficiency argument is that batteries, unlike liquid fuel, don't lose mass during flight meaning the aircraft to haul its maximum takeoff weight from departure to arrival. It's a double whammy.
Well, in this case, we don’t need to argue about theory. The Joby has a tested range of 150 miles. They also tested it with hydrogen fuel cells and got >500.
Sounds about right. A plane of comparable max take-off weight, a Piper Malibu, has a range of ~1500 miles.