If someone wants to be incognito, maybe he can mount another generic ID : Mercenary if you're IFF tag unlawful ; Trader instead of Smuggler if you conduct legal business. I read somewhere that the ID tell what is your main job ; you can change your job even for a hour.
I don't think its against the rules, as long as you have only one ID in your cargo (which will be mounted of course). As a result, a Pirate can meet his girlfriend on Manhattan and pretend to be a Trader for exemple :)
I'm not talking about Corsairs and Outcast as i think anyone of them must be proud to show their affiliation and faction, and probaly hostile to all lawful forces.