People can pass the card back over the gates, to use it for a whole group. Tou could make the software give you a better deal when riding as group or riding off hours. You could ad a cash taking machine to load money onto the card. When you leave Amsterdam as a tourist, you could have a booth to refund your credits. Just some very simple modifications to make public transport more fun for tourists and Dutchies. Tourists didn't get it with the "Strippenkaart", so at least do this one right. They said they looked at Hong Kong. Well, they didn't. Do it again!