Greg, I discovered the Religious Occupation group as separate from Religious Professions during my study of religious categories and again during the very beginning of my work to implement the religious categories principles last night. This morning I followed your wikipedia link looking for the list of 19 professions and could not find a list in the linked article. I realize now, its spread throughout the article. I recognize the traditional 3 of law, medicine and divinity, but outside that area I can only identify professions through my family knowledge which now includes accountants. Even by Wikipedia's own definition, though, my experience tells me the list of 19 is incomplete. My niece, who is studying to be a Jewish Cantor, will certainly be a professional by the Wikipedia definition but cantors are not on the list. Maybe they fit in divinity. But where are architects and types of engineers other than mechanical and civil, like petroleum engineers and bio engineers? What about physical therapists, physician's assistants and licensed professional counselors?
I consider myself to be reasonably educated (3 post secondary degrees, including a masters in library science and a law degree - so two professional), and reasonably knowledgeable about religions, as well as reasonably knowledgeable about Wikitree categories, and I could not tell you without a lot of research which religious occupations qualify as professions.
This separation adds a level of thought to the categorization process and I wonder what it gets us. There are clearly a lot more than 19 subcategories to Category: Professions, and if we combined professions and occupations, there would be a lot more than 50 subcategories to occupations which is sort of my rule of thumb on when subdivision is a good idea based on numbers alone. In fact there are already 135 subcategories to occupations. But what does a split between professional occupations and non-professional occupations get us?
Like you, I'm a fan of multiple paths and industry is definitely one path I favor for occupations. But at present, there is no religion industry path that includes all the religious occupations in a list. I think we need that. I think we need one by religion as well and the religious categories principles just adopted provide a place for that. There we abolished the intermediate level of Protestant versus Catholic on the theory that it didn't provide much benefit for the extra level of thought.
In working with the religious principles, I purposefully did not tinker with, and often incorporated the structure from other streams. So I did not tinker with the occupation versus profession split in the occupations line. I left that for later consultation. But since you are working with it, I thought I'd weigh in with my opinion.
By the way, I don't see religious orders as an occupation at all. Priest, monk, minister, nun, mother superior and abbot are occupations, but religious orders are organizations or affiliations. Yes, there ought to be a path into some occupations from religious orders, but I would not make them occupations.
As for people recreating categories we empty out, we have a way to handle that now with the misnamed categories and edit-bot process. If an emptied out category is marked as misnamed, any future profiles put in it will eventually get moved to the correct category.
If we are to keep the professions division, I would tend to simplify it to clergy, theologians, and professors. It would take too much research to figure out the ordained / not ordained distinction. Some religions like Quakers do not ordain at all but some branches do have special ministers called recorded ministers. Others like Southern Baptists have both ordained and non ordained clergy and leave it up to the local congregation to decide when to require ordination for a specific position.
If we are to keep the professions division, I think we should define clergy as Merriam Webster's Learners Dictionary does, slightly modified for our Wikitree category structure - "people who are recognized as the leaders of a religion or spiritual tradition and who perform religious services or rites."