Assuming that it takes something like 20 minutes to replace the energy used to fully charge one Leaf, a 64kWh size pack might partly charge 3 Leafs with little waiting, and, with just occasional use, be nearly "always ready".
One does lose a significant amount of energy (maybe half) in the high-current discharge, DC-to-DC conversion (vehicle-charging-current regulation), and the high-current charging.
Only a few vehicles, initially, would be able to accept the very-quickest charging rates, where overheating of cells could be significant. Even though some cell types and configurations will probably be able to tolerate 60C (one minute) charging, the 2000 amp (or more) currents are non-trivial to control, I suspect.
But, 4 or 5-minute charging (15C or 12C) would be roughly equivalent to liquid fueling speeds, where some pumps take 20 seconds to deliver one gallon.