This is long I know but - cmon read it, love it
There should be a HIDDEN thieves guild somewhere in the lower levels that holds the exclusive rights to pickpocketing - in that way thiefs must go through the trial of A: finding the guild B: getting through the high level monsters to it C: Succesfully finding the acceptance Quest D: trials of acceptance E: finally becoming a thief
This is the important part:::::::::: The Thieves\' guild members consult with an NPC which rolls a random name of either another NPC (who is not in the Thieves Guild) or player character currently in the game. The thief then has to find said character and succesfuly pickpocket them without being seen (by a spot check) - The thief doesn\'t actually take anything from the player; on a succesful steal the thief completes the quest and goes back to their guild to recieve an xp and monetary/treasure reward.
Of course such a guild would be vulnerable to attack from other guilds since afterall - who doesn\'t want to destroy a thieves guild? Just an idea but - to further refine the pickpocketing quest - temporary PvP could be added until it\'s completion or either player logs out, with the permission of both parties - this would entice the thief to be doubly careful in sneaking up to and away from his target like a real thief.
For those crazy PvP junkies out there: an assasin guild could be programed out of the same Random character selection quest with the addition of permission from the target and that no important NPCs can be targeted.