One of the problems we're faced with when trying to convert to cars that use hydrogen fuel is a catch-22 kind of thing - people won't buy the cars until they know there are enough gas stations within convenient reach, and gas stations won't add hydrogen fuel pumps until there are enough cars out there to make them profitable. The solution might be to phase them in.
Step 1 - Create briefcase-shaped fuel tanks that can be sold at convenience stores the way natural gas is sold now.
Step 2 - Create hydrogen cars that have their fuel systems designed somewhat like blade servers, where the fuel tanks bought from the convenience stores could be easily slipped into place.
Step 3 - When the exchange of these new fuel tanks reaches a high enough level, install a pump to refill them on the
convenience store premises (the way diesel pumps used to be installed off to the side at old gas stations).
Step 4 - Enhance the new fuel systems in a new model of these cars so they can be resupplied by either the blade-like fuel tanks or via a nozzle on the new fuel pumps.
Step 5 - When demand gets high enough, move the hydrogen fuel pump right beside the regular fuel pumps.
Creating a gradual path like this for switching over to hydrogen fuel might speed up the conversion process.