I'm interested in perhaps a marginally-similar issue - getting across a charging desert. Specifically Flagstaff to Cortez Co via Kayenta.
What I'm wondering is if something like this can be portable enough to serve as an additional battery backup to carry along? You know, drive to 1%, stop, plug in your device and get enough charge to make it another 50-100 miles.
Once IN Cortez, I see value in the 120v recharge because there are very few fast chargers (no DC) in Cortez, I could foresee plugging a wall connector into a 120v outlet and the battery device into a 2nd one, then recharging a bit faster in the morning to get enough charge to move on.
It would need about 50Kwh capacity and not be too heavy to load in and out of a Model Y.