(Didn't realize I couldn't use carrots... can the above post be deleted?)
I'll likely never use another non-player-driven (Literally) taxi given it's unreliable (Or was, dramatically, the one time I used it. Expensive lesson early-on), but that's a different conversation...
Perhaps since every specific keyword is separated by a linked word ('to', 'with', 'in', 'from', 'on', etc), perhaps 'steal from (container) on (person)'? 'Course I haven't seen the code or its structure so I have no idea whether (And/Or why) there'd be difficulties.
If it's purely a matter of 'faking out,' like... people RP'ing there's something in there but it isn't (Which seems to be the common concern), maybe have an ability to somehow 'know' whether the intended action is possible before doing it, without anyone else knowing the check was done (Like 'look (item) in (container) on (person)' but... requiring a certain-tier 'Thievery').
If the issue becomes that it's 'too easy to abuse' for 'every theft,' maybe only make it usable on containers and not in normal inventory. Then people can choose between containers that lock or use normal inventory if they don't want the items scoped out.
That way a thief isn't penalized (One way or another -- whether would-be success or failure) for trying to do something the player thinks is possible because of a potentially deceptive emote. Requiring the '(item)' bit means they have to know what they're looking for. It isn't as simple as "oh, what's in that bag?" and just pick something to try to take. This assuming it's not possible to just list a person's entire inventory and pick something to try to take.
... 'Course I'm of the school that likes all things custom. A pouch at the waist to hold little trinkets, utility belt for medical supplies, backpack for hiking supplies, paper bag for food, etc. Then on finalizing an item, they could pick whether they wanted it to work like a wallet or a briefcase. So I'm biased pro-tailor-container even if it's less secure (To which people'd have to choose 'lockable' or 'custom', where right now they have to choose between 'lockable' and 'not' from NPCs, which given chy and mechanical benefit, is a no-brainer).
Since I'm not a thief and all I know is what little I've read on the forum, I don't know if there's currently any difference between lockable and not, but the way things are worded regarding containers on forum, it leaves the impression there isn't really.
If I'm getting the right impression, I 'get' that the ability to 1. Know something's doable and 2. Steal from containers (Reliably) would have to be there first. And it's not difficult to observe that there're a long list of other things being worked on, so primarily cosmetic content might not be particularly high on the list.
I'm also wondering if one of the difficulties is the above: Worn containers. I remember reading that an item worn can't be stolen. I guess containers would have to have a custom rule: They could be stolen from while worn, even if the entire container couldn't be stolen.
Considering different angles, not even looking at the code, I imagine it could get... interesting fairly quickly time-consumption and testing-wise, depending on how the foundation's built. In pure modular/expandable code, it wouldn't be too bad, but I find most people don't write that way.
'Course I'm also making a trillion assumptions here, the first and most prominent being 'if there were a way around having it abused, maybe it could be discussed.' Since the concern presented was thieves not being able to get things from containers, the above glances in that direction from the few angles I can immediately think of in my half-asleep (And limited-knowledge-of-topic) mental state.