I've been enjoying a talk by David Graeber on the history of debt, and one of the main concepts is about how neighbors "owing" each other as a way to continue friendly relations predates currency and even barter. I'll post it here because it's all really interesting, and it might be something Threetoe would enjoy with his history background if he hasn't seen it already.
https://www.youtube.com/watch?v=CZIINXhGDcs&feature=emb_logoThe big picture stuff is debt is way more common and interesting than coinage. Not that I don't love people shouting in marketplaces, but once religions and cultures are more varied there are so many more cool ways of organizing than metal that is used for an extremely niche application. I've seen a lot of topics on debt on the forum but most of them are about repaying of debts rather than how good and useful people constantly owing and forgiving each other is for making stories with the people living around you. For example, you can have the interesting parts of the economic arc without having to track coinage again.
People in the fort know who their friends are, and a great way to increase the meaning in that is to have them regularly giving each other gifts. It's nice to get yourself a new bracelet but it's only new for so long for any given dwarf and then it becomes meaningless again. Having a way to gift someone with an "acquire something" desire a good mood is also one step towards a new friend. All those exchanged goods still have a tracked value, roughly like how trading works now but in exchanges over a period of time instead of barter. If someone takes far more often than they give it can be a source of drama and poor reputation, or fines imposed by the sheriff which can use the real value numbers. As people interact and exchange more it can create relationships that extend to creating inter-family marriages or other ways to become closer. Or, if the friends you're exchanging debts back and forth with are important people they can reward you with some kind of high rank or status that can.
Not only do none of these exchanges require a pouch of coins sitting around, but most of equivalent numbers them don't even need to sit in memory for long. At the end of every year the fort can simply look at all the favor owed from one dwarf to another and zero out where appropriate. People who owe a lot of debt will have it kept track of for the following year as greedy or criminal outliers that make it easy to see where Fun might arrive from. Otherwise people can keep their memories of good deals and reputations they've gained but not need to hold onto a lot of extra numbers if a fort is retired.
And, of course, all sorts of religious and cultural events, including peasant revolts, involve the complete forgiveness of debt. Generous people can forgive debts all the time and feel good about themselves for it (as they should) while the greedy should cling to their numbers much longer. Various punishments or arguments can end with forgiveness of debt or fines that replace personal debt with a general debt to the fort. A siege could leave on the condition that their debt to your fortress is erased. Why, a whole huge, and fun, part of the game can be clearing the memory of specifics and ironing them into a general reputation like it does for secret identities. Think of how fast things will run even with this little edition.
Of course that doesn't mean currency doesn't ever have a place. As in history, currencies work well for imposing taxation on conquered lands. They make a lot of sense on soldiers, criminals, and people that do business with either since they're unlikely to stick around for the system of debts to operate well. But once you have a strong enough reputation with a merchant you should be able to enter into a debt bargain with them as is appropriate for local friends. Take some fish now while you're hungry and come back with grain to share after the harvest is ready. Similarly bartenders will be generous with lines of credit for those that are well known, instead of just making everything free, creating for them an ongoing relationship with interesting people and making them centers for gossip. This way coins don't need to be in nearly as many places but actually serve better for inter-kingdom trade if a place has to pay tribute to the civ that mints those coins.
I hope you'll consider how debt and debt forgiveness could fit in with the increased role of religions and of course cultures as those updates approach. And perhaps, in some slight degree, even how they could serve as part of on-going villainy work.
