Actually, part of the "charging" standard for ALL EVs (and PHEVs) should be (have been) a car-to-car charge/fuel share mode.
Then, any other "EV" passing by could easily help another out-of-efuel vehicle.
I guess that would have helped the EV Revolution too much, so it was not included, even as an option.
Without being exotic or trying to transfer efuel really quickly, an inverter with L1 (or L2) AC output would probably be sufficient for "rescue", using a standard "portable" EVSE.
Or, perhaps a special J1772R (Rescue) AC-Output mode for the "donor" vehicle, and a simple J1772-to-J1772 "jumper" cable?
Could have been an option or even an "accessory", to help avoid the "extra cost" arguments.
Imagine one "fallen" LEAF sliding to a stop, telling Carwings of the problem and location. Then, Carwings notifies any signed-up, willing "donor"-capable LEAFs in the vicinity, and within minutes two people get to meet.
We can either decide to help each other, and even PLAN to do it, or we can wait for the Government to come rescue us. Note how well that worked after Katrina!