Doodlebug, as someone has mentioned, most people would struggle to measure what they need....I'm just looking at my boat and thinking, how would I draw something that fits to my ceiling etc (bulkhead wall).
I think you would have more success if you approached all the boat hull builders...and had a catalog of furniture available for certain boat "makes". For example, I have a Liverpool widebeam. Lets say I wanted an under the gunnel book shelf, I could go to your website, click on "Liverpool widebeams"....see a few bookshelf designs, click order, and receive it within the week.
This is the only way you might achieve mass orders, regularly. It would revolutionise the boat building industry, as many boat builders would buy direct from you. You would need to have a wide list of available products on your website (but no stock, as you can make them on demand?)
Here's a list of things I'd expect to see on your website
1. Bulkhead walls
2. Bed frames
3. Clothes cupboards
4. Kitchen cabinets and layout designs
5. Ceiling feature beams
6. Microwave and eye level oven cupboards
7. Walling, and ceiling boards, with the trim bits to cover the joins
8. Wiring conduits along the floor, or up on the ceiling
9. Saloon tv/DVD shelf
10. Saloon L shaped sofa
11. Dining nook, table, chairs.
12. Hatch doors and frame
13. Roof boxes
14. Generator boxes
15. Battery boxes
16. Cratch seat/storage
17. Porthole frames
18. Window frames
19. Shower enclosures
20. Bathroom/sink enclosures/cupboards
Even if you specialised in one small set of boat hull designs, you could cause a bit of a stir....One of the benefits I imagine is that you could also branch into using various types of materials to suit peoples budgets....oak, plastic,..ply...
Most things which cause problems on boats are:
1. The slant anf height of the under gunnel wall.
2. The slant and height of the above gunnel wall.
3. The curvature of the roof
One you have the blueprints from the boat builders, you have a business
You could even have a full set of furniture/layouts designed for different boats...eg a 57ft Liverpool widebeam. People could buy a sailaway and order a "kit" from you.