Now you have to carry the diesel inside the cabin. I have no idea what the efficiency is, but I have to assume diesel generator->electric battery is going to take a sizeable bite out of the energy budget. At that point why not just buy an ICE?
>Now you have to carry the diesel inside the cabin.
Or have a trailer with the generator and fuel tank, I always thought (if we can depart from the "ideological" part of EV vs. ICE) that it could be a "standard" range extender for any kind of electric car, a sort of hybrid on demand, you normally drive (short range) an EV and if you have to do a longer trip you rent the trailer with the generator set.
I know with the Leaf that would be relatively easy, because it doesn't ensure current from the battery matches the current going to the motor, so if you add a plug into the HV and inject power so the battery current nets zero, it can drive indefinitely. The gen2 (non-plug-in) Prius throws errors if it detects current out of balance so it's a lot harder to hack. So whether any given car could easily be hacked to use a generator is up to the particular implementation and us hackers don't have those Rivian vans! Though, I wonder if anyone has hacked the pickup yet?
It'd be for emergencies or maybe the one planned night you can't charge from the grid. Same as those primary-EV hybrids, it's just that you wanted this specific truck that happens to be full electric.