Check out Moultonboro airport 5M3, I believe you can land in the pond/ lake next to the airport and taxi onto the airport, or just land at the airport. The airport is a great resource, I met a pilot and the owner there Friday when I landed there for the first time. It's about 10 minutes to my home on the lake in Moultonboro. Also you may want to call the owner of the airport who is there most of the time. He may have some ideas for you. Best of luck.
Edit:
There are homes with ramps to the water that were probably put in before all the rules and regulations, some might be adequate for your plane, then obviously you would probably need to build what you need. As long as you don't insist on having the plane right next to the water you may be able to have a hanger with a ramp to the water. The other option would be a dock with a cover over it, which if you purchase a big enough lot should be doable.
Edit 2:
Check this one out, I see a ramp that just may work in the picture, you would have to build your hanger further back than your pictures, but I doubt you'd get something like that approved in NH anyway:
http://www.lakesregionhomes.com/Prop...TIAL&OfficeID=