A small trailer with a Honda EU2000 generator and 5 gallons of gas would take you camping or on a several days outing. A 200W PV panel with maybe a 300W inverter wouldn't hurt and would fit on a small trailer too.
My buddy camps like that. His F-150 is so packed out, that he has to tie stuff on top of the tonneau cover, he was telling me last night that he just added a house battery system, with dedicated inverter and automatic charging relay. His camping stuff is in dedicated tupperware bins, ready to go camping at a moments notice. I've looked into these on occasion, there's stuff in there that looks like it hasn't been pulled out since Carter was president.
I'm on the other end of the spectrum. I'd be more likely to carry a 30 foot extension cord, camp on the spot right next to the stinky bathhouse, and run my extension cord through the bathroom window at night for my next days charge.
No word yet on the "pony" battery cost, but possibly in the neighborhood of $1000?
Sondors makes a nice, removable "triangle" pack for some of their E-bicycles, so I'm sure they will come up with a nicely designed and engineered package, eventually. The Metacycle is a 72volt system. Right now, $1000 would buy you about 6.5 Kw hours of these generic, 36V 30 Ah batteries,
https://www.ebay.com/itm/393182339879, which is 150% of the capacity the machine comes with.
Personally, I'd be disinclined to shell out for that add-on, the 80 miles of claimed stock range is a week and a halves worth of riding for me. I ride almost everyday, but I ride more than 100 miles in one day only once every 3 years. I think there are a LOT more folks like me, than there are Iron Butt riders, they just don't join forums to talk about what they use to get to work and the grocery store. It would be like joining a forum to talk about your stove or your clock-radio.
This little scoot is no touring machine. In my view, no E-vehicle is, .... yet. Even if they never are, they can still manage probably 80%+ of the world's transportation needs. And with increasing urbanization, that number goes up, every day.