We were staying at Meidera Beach,FL one time and the only place to launch my Tandem Island was over a 4 ft seawall, what a pain that was. What I did was lined up the sail, mirage drives, AKA bars, and AMA's on the sea wall. I then lifted the back of the kayak over the sea wall (the wall was about 1 ft above the parking lot, but on the other side it was 4 feet down to the water. I then grabbed the bow and slid the boat backwards down into the water, I then climbed down and grabbed all the components off the sea wall and assembled the boat in the water. It actually wasn't nearly as bad as I had imagined. When I came back I did the reverse, lining all the components up on the seawall, I then grabbed the bow and lifted it onto the sea wall, I then dragged the boat out of the water. It scratched up the bottom a little dragging the bottom of the hull on the seawall, but it was suprisingly easy since you are never lifting more than half the weight of the boat at any one time (about 50 lbs). I'm pretty sure I would not have been able to pull the assembled boat over the wall.
Another time we had a campsite at Bluewater RV resort down in keywest that had a dock. But the dock was about 4 ft above the water. I did the same thing to get the boat into the water. Fortunately we were there for a whole week so at night, I would just park the rigged TI at the dock, then go out every day. It was just a short paddle out the canal out to the atlantic so we had great fun.
You might want to look into what I did at Bluewater, when your using the boat often, just leave it parked at the dock.
To get it there initially I would look into launching the boat at a more convienent location close by, then sail it to your dock, then just use it for the duration of your stay, docking it in the water at night (remove your sail,mirage drives, and paddles, plus anything valuable). When your done for the weekend or the week, just sail it back to where you launched from and load it back to your vehicle.
Alternately if it's your dock, or you can get permission to do so, you can get or make a small crane to lift the entire boat out of the water (thats what I would do). If your creative, you can probably build the crane for under $100 dollars using a manual winch. You are only lifting a couple hundred lbs, so it doesn't need to be anything fancy (2 inch steel water pipe would probably work fine, then add a cable or belt manual winch, like they use on boat trailers (you can get them for $20-$30 bucks at places like Harbor Freight in the US).
Just some ideas