I hate to say it, but does this mean the the lowest budget, lowest tech. version of a stationary L3 charging station would be a lousy ~60hp ICE driving some floor mounted rollers ala a chassis dynamometer (but without out the need for the expensive power measurement bits of the dyno) to pump 30-40 kW into the battery using regen? That's one way around the limitations of the 3.6kW charger. It would be frowned upon by Nissan to be sure, but I wonder if they could legally void the warranty, since a long steep downhill road is an identical experience from the traction system's perspective. The roller system could all fit on a portable truck which would also probably be a way to weasel around stationary engine regulations. For an off the shelf solution with extra crazy points, picture driving the front wheels of the Leaf in the tire crotch of a fenderless dual axle truck on jack stands. The tire track width would almost certainly not match, but with any luck the interior pair on a 18 wheeler tractor might just match a smaller car, and you could use the cargo ship tie down hooks on the Leaf to anchor it from popping off the driven wheels (see, safety first).
It would at least be amusing to see the well to wheels efficiency and CO2 impact of the engine driven roller approach vs. various grid power plants with all the associated losses, etc. I don't like the idea of resorting to hydrocarbons, though (even if they could be a magic sustainable biofuel), so here's what it would look like if you installed a municipal style water tower over the roller charging station to power it in a pumped hydro storage fashion. Dump 100 liters/sec from a tank elevated 40 meters and you get 40 kW of water power to run the rollers directly off of a Pelton wheel (back to 19th century technology!). Of course you need a 1800 cubic meter (475,510 gallon) tank top and bottom to hold enough water for a 30 min charge at 40kW which is no modest infrastructure for one lousy L3 charge. They you have to figure out where you're going to get your power to recharge the 20 kWhs of water back up the tower and how fast you're going to do it (duty cycle). You could buy renewables off the grid, or have on site solar/wind, but it looks pretty clear that the amount of infrastructure involved doesn't justify the modest service provided. Maybe it would work in New England where they could resurrect all those old mill water power sites as EV charging stations.