This looks so SOLID, Im happy to see its progress.
If I may, I would like to suggest something that I think would add a whole lot more to the cash system.
It should be simple because I was able to code and patch it together myself with a few mods on a SMF forum.
It was a simple 3 mod hack job:
(There was also a Bank system)
I I took the store system, and called it "The Armory"
I created store items, as GUNS.
Under the hood, each gun was realistically a One time use "robbery tolken"
So my users could buy weapons with their cash, and use the weapon to gain/steal cash from another player. the weapon would be deleted after one use, regardless if it was successful.
I could set the chance% and max-min value a "Item" could take from another user based off their personal savings. Users would have to put their cash in the bank in order to keep safe.
I was also able to create "Items" with permission properties, or safeguards from attacks.
So users could also buy a whole range of other items, and they had the option to buy or give items away to anyone.
**edit** some items where also cosmetic, could reward other things like reputation, some where a one time use where others had multiple uses.
The store would feature a IN STOCK system so I could set how many things where availalbe before they could no longer be bought and had to be restocked.
this made it fun to create rare itmes that people where afraid to use up or give away because some would rarely go back in stock.
The coolest thing about it was that when posting, not only could you see how much cash you had, but you could also see the 3 last items you bought, each item image has set properties so they could display properly in the user profile area on a post.
People could see your small arsenal, and if a user happend to have a really expensive gun with better chance and higher amount, it made you think twice before you would start an argument (If you really cared that much about your cash). It was hilarious.