I know this is a tangent away from stealthmode, but as far as the spymaster is concerned, what about the ability to send anonymous messages to individuals/groups?
If they themselves cannot be hidden, perhaps they can start to hide the source of information/misinformation they leak?
I like the idea. The question is, would they be able to reply? In RL, they could give the messenger a letter back but it could have been left somewhere instead of a direct deliriving so it could go either way. Maybe an option for the sender.
