What is the possibility of developing e-permits similar to the e-tickets you get for air travel.
It would be great to be able to get your permit prior to leaving home. You could pay by credit card, acknowledge and agree to the rules, print out you permit, print out your parking tag, and have everyting ready to go before you leave home.
There would be no more showing up to find that an access point is full. You would be able to enter access points without a ticket office without treking out of your way for a permit (eg #13).