Well then, to keep it "Simple", change it to 'any spinnaker boat has right of way', period. Then in your scenario, C has right of way over both A and B, and A had just better get out of the way and B can tell A he's got to have room to keep clear of C.

I don't know the history of when and why the "Leeward boat has right of way" rule was written, but I'm guessing whom ever wrote it never envisioned a fleet of spinnaker cats coming downwind at nearly 20 knots...while one boat is going upwind yelling he's got "rights", as if the spin boats can hear him anyway, or can do anything about it, when the puff is on.