I haven't actually had a character that is a thief, but I was thinking about disparities in FK roleplaying opportunities due to class yesterday. It seemed to me that adding some rogue/thief skills that were cooperative in nature would help foster roleplaying of thiefly actions:
LOOKOUT- a character acting as a lookout could have a limited ability to alert a character that is in a nearby room: "You hear Feeb Longfingers cough." Other characters may or may not hear this, since it would obviously be an understated signal.
SIGNAL - The problem with Thieves Cant is that it is a real language and it is obvious when someone is using it. A thief should be able to visually signal another in the same room (or all others in their group?) using a much more limited vocabulary. This could be implemented by allowing a limited message (say eight characters) to be passed if the communication works: "Feeb Longfingers signals 'MeetFont.' Again another might intercept the message and either see "Feeb Longfingers signals Greecy." or the actual message, possibly scrambled as if it were a regular language. Or maybe the thief would only have a limited number of generic messages they can send, as per socials (Meet at hideout, steal coins, follow him, etc.)
DISTRACT - A thief's assistant should be able to distract a potential victim to allow the thief a better opportunity. By issuing a command like "Distract citizen" the citizen could have a reduced change of foiling a steal or backstab in the next round or two; if it failed their chance of foiling an attempt would be improved, because they are suspicious.
COVER - If a thief fails at a steal, an accomplice should be able try to to "rescue" the thief, allowing them to flee the engagement more easily. There would be a chance that the accomplice would instead be engaged in combat or tagged as the lawbreaker. It might also work to limit movement of a mob in a particular direction (i.e. into a room where a thief is working).
Some of these skills could would work like sneak, where one is covering/alerting a particular individual until the command is turned off.