So now we only do one action in a turn?
EDIT: How about we (try to) apply something like gold standard system?
The currency (coins) would be worth only as much as the goods (or just rings) that you keep in your safe? That would allow for complex calculations like "How many coins do I want to emit? How much do I want my coins to be worth?" etc.
That'd also implement inflation and exchange rate calculations, which might either be good or bad, depending on what one likes.
The way I understand it, the "worth" of any currency is its exchange rate for resources. Caravan wealth (ie: "fiat currency") is an agreed upon, easily transported intermediary for what basically amounts to as the barter system. The vanilla Dwarf Fortress trading depot is your basic barter system, where resources are exchanged directly - wine for luxury items for instance. The luxury items are only worth as much as they are in the Mountainhomes because supposedly they can be bartered for other resources such as food, wine or stone.
I think the reason we used to use the "gold standard" in RL is that gold was relatively rare, didn't rust and could be pressed into coin molds with more ease than other types of metals or substances. The amount of gold in circulation around the 1500's was finite, so that the worth of a certain weight of gold vs some good or item was able to be determined on a relatively certain scale - the coins became barter chips for the worth of goods.
Of course, the Spanish finding all that gold in the Americas increased the amount of gold in circulation, which meant that for a little while they were able to exchange those new coins whatever resources they wanted, but eventually the exchange rate of coins for goods rebalanced with gold coins being exchanged for far less than before. The "Midas touch" exploit would do much the same - a short term increase in buying power followed by the relative worth of all gold coins being devalued by everything requiring a greater number of them to buy anything.
My thoughts were this: since rings made out of gemstones (rather than just metal or stone rings encrusted with gems) are unable to be requested from Non-Player Caravans, and only get produced rarely even by high-level jewelers, plus the fact that they are intrinsically worth up to 300db a piece and easily transportable made them a viable choice for a possible currency between civilizations. Part of the reason that new embarks are not allowed to bring anything with them is to make everything that is traded in the game have to specifically exist somewhere already - otherwise an unending supply of stuff and resources would make Players only want to trade those rarities that couldn't be brought on embarking wagons like FB bones or artifacts. (Neither of which are needful items - they would only have value for the Players that were collectors of rare items.) Depending on how much gold, silver and copper was found, my thoughts were that coins would make up the differences in value between one ring and another (and sometimes be taken out of the trading system by Players who needed to melt down enough to make a gold bar for some artifact demand or something.)
We already have a "dorfbuck standard" from within the game, but how much each good "costs" would be made in any bids that are posted for resources, which is entirely up to that Player. Eventually the amount of coins and rings that Players are willing to spend for certain goods, vs what Players are willing to risk transporting should even out.
Really,