Actually it's pretty easy to implement pocket picking.
Just create a few random loot tables based on victim class/wealth/whatever and when sucessful you get a piece of random pocket loot. A few coins, a ball of lint, a lucky rabbits foot, whatever. If desired you can place rare/exotic items in the loot tables (not a good idea if you ask me, but that's my opinion) and the fact that they're generated at ramdom means X NPC doesn't always have Y item so you don't get "Must rob X NPC everytime you play the game because it's the only way to get Y item."
It won't be "Must rob X NPC every time to get Y Item" it'll become "You must pickpocket every NPC everytime to increase the odds of getting Y item until you get Y item (unless you can pickpocket 2".
But that really wasn't my contention on the difficulty of pickpocketing - my contention is to successfully simulate pickpocketing (IMO) you'd need to consider facing, victim-NPC awareness, other NPC awareness (particularly Johnny Law), which pocket was to be picked, what size/weight the item was before ever being able to calculate success.