First off, Meph, keep up the good work, the humans are really making me curious now.
Now for the (late and general) criticism:
As far as I can see, money is generaly a very important factor in the average human fortress. Yet, I feel that money never really fits in the df universe. The simulation that is dwarf fortress, lets you take on the role of a purely producing and consuming economy, the only exchange of goods is through "item for item" trade with caravans (at least in vanilla df), and everything in the fortress belongs to you and can be freely disrtibuted (except in some noble situations). Wealth is being counted anyway, you don't have to amass piles of gold coins in your chambers.
The actual problem I see with putting emphasis on using coins and "money", is the following. Depending on how much gold you mine, you can make more, or less gold coins. Fair enough, in medieval times it was probably somewhat similar. Still I feel like something is "wrong", if you can just mine for gold and print your own money to eventually buy stuff with that. Basically this chain of production is the same as mine for gold, make masterwork gold bracelets, and profit (through caravans). Increasing the importance of coins also creates the impression that there are actually two seperate "currencies" in your fort; coins and "items".
Now, as far as I can see, humans even have plenty of reactions to create coins from not-mining, so maybe that's not that much of a problem.
Also, this is not intended to belittle your ideas for the humans, I just wanted to give my two cents. I hope I could somehow show what my problem with coins in Dwarf Fortress is.