I don't see a disagreement here - all your examples are great and work perfectly well. Waiters and sales-people also have to assess the costumer and behave accordingly - whether to be authoritative, friendly, more submissive or...   

My point is that the types of people I mentioned actually DO have similar skills, so that if they were educated in law-enforcement could be put to great use. I am suggesting a new type of recruitment strategy that might not be so obvious, and you yourself stated that you had problems recruiting... Its worth a try is what I'm saying.