Pickpocketing should have a size and/or weight limit, that way swords, armors etc. big and expencive stuff wouldn\'t get stolen.
The limit should naturaly increase as the skill increases, but never too high...
And also thieves should not be able to steal things that person is wearing...
Other possibility is that if someone ois trying to steal big and/or heavy items from other person, then people surrounding the victime recieve a message saying something like: \"You see a thief stealing from [insert name here], and then they can kill the thief.
One idea about thieving is that if city guards or smth. like that notice it they would come and fight the thief, but if thief loses, he/she will spawn in jail. And then he/she can pick the locks and escape, pribe the guards, maybe dig a tunnel

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