I'm not sure for unofficial jobs like those, but I know claiming one-off positions for NPCs is typically not permitted (i.e. you couldn't say your character's dad was head of a Ministry department, only a "upper-level Ministry official"). NPCs, with the exception of some inactive characters who have a long history on the board in a certain position, aren't usually listed on the occupations list, though (and even that might not be intentional :P).

Don't take my word for it, though :P