Wouter, having read your post I do understand why you feel that ISAF recognition is not important, though I`d just like to share my experience : I have contacted ISAF about getting a recognised handicap for the Mosquito, and found their response to be helpful at all times. I have been unable to get the Australian & South African Mozzie class officials to agree on certain points, and have thus been unable to submit the info to ISAF for inclusion in their official handicap list, so we have used their formula to establish an unofficial ISAF h/cap used for open class racing in South Africa only.
The down side of not having ISAF recognition / backing is that when competing in open class events, we submit our handicap rating to the event organisers, including the ISAF spreadsheet with all our statistics as supporting evidence, only to find that the event organisers in many cases have "adjusted" our handicap to alter the results whenever we appear too high up in the finishing positions. In most cases this occurs because the event was organised / run by the Hobie class association, in which case it is in their interest to see their own boats filling the top positions.
(The Dart class has avoids sailing with us for fear of embarrassment).
My feeling is that if we had an official ISAF handicap, no event organiser would be able to behave in this way without serious repurcussions, as we could take the matter up with our own controlling body, as well as ISAF should this become necessary.
Furthermore, in your situation, in order that sailors in other classes take us seriously, I feel that it would be important to gain ISAF recognition and inclusion. I know that there are costs involved & obviously if the support base for the class is currently too small then it may be something that we work towards in the medium term, and in the short term have unofficial regattas, but we should always try to run the class in a manner which does not seem like a renegade class which is trying to avoid the systems in place which could ultimately help us to grow.
Just my opinion, beat me with a wet fish if you disagree.

Steve