What some ops seem to do is have a trailer with a large holding tank(s) which they fill at an off site compressor and then drive to near the boat and fill all the individual tanks in situ.
Having worked in Grand Cayman I'm not a big fan of this, although I can see the advantages you mention. The biggest drawback is that in-situ filling from an air trailers tends to take quite a bit longer than swapping tanks out.
Not really an issue at Yacht Club where each boat has its own spot, but at West Bay Dock where multiple operators use the very small dock it can be an issue. You can end up with boats 'hogging' the dock while filling (even with all operators trying to work together as best they can), especially at the busy times when all the boats come in and depart.