Now here's an idea. How about deliberately disconnecting some of the marinas from the network, or indeed filling in some berths to make hard standings. Then provide a cost effective way of lifting boats in and out. People who only use their boat once or twice a year would then not need to licence the boat all year round.
If the cost of a lift in/out and two weeks visitor licence could be made cost effective, I'm sure many boaters would take this option.
Martin Brooks