As I wrote earlier, all current formula classes have limiting DESIGN factors, ultimately creating boats which have an EQUAL definable PN number, or ISAF rating. That`s the core of Formula classes, that everyone`s boat can be different, but they have EQUAL (or very similar) performance. Move away from this concept & you have lost the plot.
After reading all the posts involved it seems VERY clear that all interested parties want to be able to experiment, some want to build from scratch, some want to "hot-rod" an existing boat.
I`d suggest picking a PN/ISAF number to work to, and make that the ONLY rule. Any length boat, any size sails, mast, number of hulls, number of crew, as long as the boats all rate the same, it`s first man home takes the trophy.
Make it INCLUSIVE, not limited to one type of boat. This will also help contain the costs for all. Nobody has to cut bits off the end of their 15ft boat if it has the right rating.
The spirit of the class should be to race on equal footing at low cost. Pick a PN number that is a little ambitious for a 14ft boat, but not so wild that you have to modify the hell out of a boat, or overdesign the rig to be competitive. Base it on the average of the 14ft designs that you have sailing currently with added spinnaker / hooter. Good idea to base it on that H14 that is on steroids.

Cheers
Steve