I think this is an admirable effort, but making a distinction between the tagging of voluntary professional associations and mandatory professional regulatory bodies is going to be extremely difficult and, in my opinion, probably not worth the effort.
To me there are chiefly two obstacles to a consistent, unified tagging scheme for this: 1) differences in terminology from jurisdiction to jurisdiction are contradictory and confusing, making it difficult for anybody outside of the professions to distinguish them, and 2) in some jurisdictions, in some professions, there are no real distinctions between the regulatory and advocacy associations anyway (which you’ve already pointed out with the remark “Sometimes 1 will also do some of the same things as 2”; e.g. the Association of Professional Engineers and Geoscientists of Alberta (APEGA) is a mandatory professional regulatory body created by legislation, but it also acts at the profession’s advocacy group). I also suspect—but admittedly have not verified—that there are places around the world where membership in the advocacy organizations is mandatory (making them more akin to a union), and places where membership in the regulatory body is optional, blurring the lines of how to distinguish them.
To illustrate the first obstacle let me use lawyers as an example. Sticking with Alberta, the professional regulator for lawyers is the Law Society of Alberta, while there are several professional advocacy associations in the province; the largest of these is the Alberta Branch of the Canadian Bar Association (CBA–Alberta), but there are also smaller associations such as the Calgary Bar Association.
Generally in most of Canada we call the regulatory bodies “law societies”, but there are exceptions: in Nova Scotia it’s called the Barristers’ Society, and in Quebec it’s the Bar of Quebec (Barreau de Québec). The advocacy organization in Quebec is l’Association du Barreau canadien–Québec (“Canadian Bar Association–Quebec”). Again, just to be clear: the regulator in Quebec is le Barreau, while the advocacy group is l’Association du Barreau. 
In neighbouring New York the advocacy group is called the New York State Bar Association. However, the “state bar”—the regulatory body in New York—is an office of the judiciary itself, not a separate self-governing professional body. Lawyers in New York must register directly with the courts system to practice. (Disciplinary actions are carried out by the Office of Court Administration.)
This stands in stark contrast to many other US states where the “bar association” is both the regulator AND the advocacy organization (like the example of APEGA above). They are thus said to be “unified”. This is similar to how it works in England and Wales, where the General Council of the Bar works as both advocacy group and regulator; the regulatory functions are carried out by the semi-independent Bar Standards Board. However, membership in the Bar Council is not mandatory, whereas American “unified” state bar associations are mandatory. The Bar Council is also only for barristers; the UK still separates barristers and solicitors into distinct professions. The equivalent for solicitors is the Law Society, and the Solicitors’ Regulation Authority (SRA); again, membership in the Law Society is not mandatory, but solicitors’ practice is regulated by the SRA regardless of membership in the Law Society.
Again I would submit that these distinctions are not very important to laymen looking for an office location on a map, and I don’t think we can fully convey the subtle differences in whether the regulatory bodies and advocacy organizations are separate or combined, mandatory or voluntary, self-governing or an agency of the government, etc.
office=association, association=professional seems perfectly reasonable for both advocacy organizations and regulatory bodies, except perhaps if the regulatory body is an office of the government itself. In that case I’d go for a combo of office=government and government=regulator or something like that.