I guess you could strap a few kw generator in the bed with some jerry cans as backup. Would take longer, but if by loiter time you mean time out in the field where you’re not moving, then maybe that’d work. Would be cool if there was the equivalent of siphoning gas from one to another.

Is there electric infrastructure in the places you’re describing? If so, should be really easy to throw down some moderate-speed L2 chargers in various parts as a last resort. They’re incredibly cheap and don’t need much maintenance.