Sam:

For those of you in areas where there is enough of fleet to run regattas and keep the "family" together by all means stay under the Hobie Cat umbrella but demand real support from those who have placed this constraint on you. You'll need financial assistance (Yes real dollars) to offset the loss of the X boat fleet if it was substantial...that or you will have to raise the race entry fees to what will likely be prohibitive levels.

Get together with your friends (See also fleet members and x boat members if you all get along) and vote on what you all want to do.
No one can stop you from having an "H-16, P16 and N5.0 fleet" and we all know what those designations mean. Anyone who says they can ban you from a nationals based on your performance as a volunteer in a non profit organization had better consult an attorney because it's illegal to ban your entry in this state for at least two reasons.(Ask your attorney for the details in your state).

In the final analysis you and your friends (FRIENDS: that is after all why we sail as groups isn't it?) will have to decide if they want to extricate people based on their brand choice or if it is really your intent as a group and as individuals to share in this experience we call catamaran sailing for the benefit of the sport as a whole.

Set out a spread sheet with PRO AND CON and see what your national/international organization does for you and decide whether that warrants playing but what they describe as THE RULES.

Sorry, THE SAILING RULES are written by ISAF and everything else is a class rule and nothing more. You can adopt them for your sailing instructions based on your SIs --- or not.

I fully understand why Hobie Cat only wants to provide support, funding and an international organization to oversee their boat's class racing and they have every right to do that and probably should. What you have to decide is whether or not your group of friends wants to participate in that full time or whether you would rather just participate in that occasionally at the national championships.