When I was at the Nissan leaf demo a few years ago in NC they had a fast charger that was going to be installed at best buy so you can shop and get a 80% charge at the same time. They could install these at rest stops or fast food places and you can fill both tanks at the same time.
I guess plan B could be a retro fit kit to go to a fuel cell and offer hydrogen fueling stations or something?
Maybe to make it more universale the hot swappable pack for extended trips could be trailer mounted? Seems any car can get a hitch and has some towing ability. Then all you would need to is wire up a plug to your original pack and match up a towable one of the same voltage.