Hahah, awesome idea. In the past I wanted to stick phones to the trees in the random forest and made my own onion mobile phone network. But cars are better because moving all the time.
When I think about it, rental e-scooters would be probably even better.
These scooters already have modems on them. Hah, hacking them to be a mesh network (although I guess not many have WiFi/Bluetooth), sounds like a plot device for some "hacker" movie.