Turns out I shouldnt be posting reviews when Im having a bit of a manic christmas stress episode. Sorry y'all! Apocalypse averted.
So anyway, to properly review this thing.
Hidden Pocket does by itself a relatively weak thing, +1 hand slot. It does not change the board state but enables more flexibility with weapons and tools. Hand slot tools universally take 1 slot, so the point of extra slots is all about enabling greedy strategies with 2-slot weapons. Ornate Bow comes to mind. The illicit requirement is'nt much of a drawback, but "I'll take that!" can help with this issue.
In an older version of the game, or with a limited collection, this would be a very, very bad card. Card draw used to be a premium that only had. Wasting a draw to find Hidden Pocket with a core+Dunwick Jenny Barnes would be like shooting yourself in the foot. The reason it'd be so bad is that a card like this needs a strong, dependable flow of cards to find all the pieces. You need to find the clothing, find the weapons and tools, find the pocket, find money generation to pay for it, find the card draw. For a large swathe of characters this is a ridiculous stretch.
But the support does exist, and the synergy, particularly if you have Underworld Market which single handedly assays the card's downside of dudding a draw and the deckspace issue. Also of note is the synergy, not only can you use Pickpocketing to fund the expensive boardstate, you have good illicit hand assets like Thieves' Kit to put into the extra slot.
I misjudged this card first time around. Even so. It is -very- niche. I wouldnt reccommend it for most decks without careful planning.