I like to add that pickpocketing should be taken as bonus action ... in mine opinion.
It seem incredibly stupid that my rogue-thief can steal all merchant's stuff within single turn (aka. 6 seconds) ... flash will blush about their speed. :-/
But if it will be threated as bonus action ... usual character can steal at once half items than tief, with seem quite accurate.
Then every turn vendors can roll perception ... preferably with lowering dificiulty.
You know ...
one thing missing > dif. 20 to notice
two things missing > dif. 19 to notice
five things missing > dif. 16 to notice
etc.
And for very lucky thieves:
20 items stolen > dif. 1 to notice ... aka certainity.