Have you looked to the kit car industry to see which makers have been successful and why? I believe Factory Five Racing has built a very successful paradigm in the Cobra kit car market. The kit is intended to use the drivetrain from a donor vehicle (Mustang) which dramatically increased the range of potential builders by simplifying the build process. So your comments on using existing rudder assemblies and such are right on. Actually be able to tell the builders what ones work and how to attach them. Obviously the Hobie line is an excellent source.
I would even suggest contacting FFR and picking there brains on their ideas on what worked and what didn't. Including marketing- which probably be the biggest hurdle.
