Would it be a good idea to ask the particular boat companies to "sponsor" a particular class for the event? This would seem like a fair idea, as it would allow more sailors to participate (with several classes), as well as defray some of the financial burden (of additional staff, logistics, etc.) to the major sponsors (Tybee, Rolex, or whomever). The mfg. could specify which class (like the Hobie Fox class, the I-20 class, Marstrom 20 class, etc.) to add to the NOR, and the organizers could (at their discretion) add an "open" class or formula class.
If boats of widely different d-PNs are used, I guess one option would be to have staggered starts, with the slowest off the beach first in an attempt to have them all finish at the same time to save the poor RC from having to sit all day (or several days as the event progresses) judging finishes.