I have to disagree with separating them like SA:MP does. It's very confusing to players, and honestly "/duty" has nothing to do with police itself, so I'm still confused why they received that command, but everyone else got their job's named after the chosen career. Also, /fireman may be short and simple, but it's honestly quite sexist to female players. The politically-correct command would be /firefighter.
Anyway, IV:MP, through Squirrel, is capable of GUI's automatically coming up upon entering an icon on foot, just as SA:MP is now in PAWN, and Liberty Unleashed also is with Squirrel. Why not just do that so new players can walk into the icon, make their selections via the GUI, and be on their way to roleplaying? The help dialogs then would only need to tell them where to go. This would simplify every job immensely, would appear highly professional in the server, and would be much easier for new players and non/broken-English speakers to understand.
IV:MP is already capable of this, and it has actually been advertised by the IV:MP Development Team on their website. I'm actually quite confused why these sort of things aren't being done from the start. They are much cleaner and simpler to the players, and their appearance is much more professional and customizable.