I have held membership in many class associations as well as several yacht clubs over the years and there has never been any restriction as to who "qualifies" for membership - you pay your annual fee and you are welcomed. There has never been any problem (perceived or real) from any "pressure" group trying to influence the association/class/club one way or another, the majority of the membership has always been "members" who had the best interest of the organisation at heart and any "trouble makers" were always seen early for what they were. It would just seem to me that to make membership "conditional" on ANY criteria (other than being financial) just tends to limit the interested parties input and suffers the risk of making it eletist as well as limiting numbers.
Any membership fee doesn't have to be "restrictive". It doesn't have to be $50 or $100 or $1,000 per year, it could be a nominal amount just for the formallity. If, to become a member it was required to pay an annual subscription of, say $15.00, it then formalises a persons membership but it doesn't inhibit anyone from actually joining, and then the only way to have input into the "running" of the association and to be able to vote would to be a paid up financial member.
Thats the way that associations have worked "forever", do we have to reinvent the wheel??
If you really want to change the format of the association away from the way that you have formed it Wouter, and bring it into line with all other "formalised" associations, then there is no other way than to go down the track of having a constitution, class rules, and regulations. Trying to make
"membership" dependent on this and that, but having no constitution etc or annual fee, is fraught with so many pit falls that it will have you waking up at night in a sweat thinking " Oh why, why, why."