The problem with coins is that each stack of coins that is minted has a specific set of data associated with it. You have something random minted on the face of each coin, where the coin comes from, when it was minted, etc.
This means that if you spend some of those coins, it doesn't become just another gold coin in the pocket of the merchant, no, it has to be tracked completely separately from every other coin that merchant has because it has a totally different thing stamped on the face of the coin and where it was minted, and other bits of data to track.
Give that stack of 500 coins a chance to circulate, and you wind up with individual coins being kept separate from all other coins. Oh, and even worse, they can't be stacked together with other coins in containers, so your fortress just becomes littered with individual coins taking up entire tiles of the floor, each belonging to a different person.
Even if a dwarf manages to find two coins that came from the same stack in the first place, there's no way to consolidate those coins back into a single stack of coins.
And then, dwarves have to carry those coins. And they can only carry one item at a time.
Basically, letting dwarves have coins shut down your entire fortress as dwarves started walking back and forth carrying individual coins from the floor of the dining room around to buy a single plump helmet, and then toss the plump helmet spawn on the floor, because nobody can be bothered to pick up the tremendous amount of trash strewn about your fortress.
While hilarious, that's a mess that should not be repeated. Coins should be nearly invisible to the player. A dwarf should be able to "wear" them like clothes and not have to haul them like they're furniture. One copper Kivish should not be any different from another.
Reading into some of the threads you linked to, I see players sharing ideas to make coins useful, while I'm thinking the other way around. Money facilitates trade, so dwarves should have money.
Hence, nobody minted coins. Dwarves still had their magical invisible credit cards, where they simply were attributed a certain amount of wealth by the fortress for having done so much work, and that actually worked somewhat as an economic model, although having artificially fixed pricing on everything kept everything problematic.
Basically, it just wasn't a terribly good system.
Fixed pricing breaks the system. I mean, players should maybe be able to set prices on certain things, but interdwarf trade should be based on prices achieved through market clearing.
I've spent many years learning about and contemplating the implications of economic theory and have an extreme interest in evolutionary psychology. Dwarves are not humans, so they may honestly be so impressed and pleased by waterfalls and ruby-encrusted chert thrones that they don't care about their dead babies, but then they do enter strange moods from time to time...
Well, I had a discussion about that earlier, in the Class Warfare thread and the spin-off I, Dwarfbot discussion about maknig dwarves have more complex personalities and autonomy so that the economy could be made more meaningful.
Thing is, you have to make dwarves more autonomous and have more complex demands and desires to make them more capable of participating in the economy. Otherwise, they're just buying rock mugs because they have rock mugs in their preferences screen, and then throw them on their floors and never touch them again.
Of course. A dwarf should buy a good or take any autonomous action to achieve his most important unmet want that he can do anything about. If he wants a rock mug, buying one should satisfy whatever desire made him want it, and obtaining another one should be much less important.
I like a lot of your ideas, particularly about dwarves comparing their wealth to other dwarves. I think priorities should look something like this:
1. Immediate danger - keeping a safe distance from a GCS is more important than picking up the sock of the dwarf it just killed
2. Hunger/Thirst - when building a wall, make sure you end up on the side that has food and drink on it
3. Security - a dwarf that afraid to fall asleep (whether his fear is of a real or imagined threat) is an unhappy dwarf
4. Basic socialization - An ostracized dwarf is an unhappy dwarf. A dwarf whose husband just died or cheated on her (if that were to ever be part of the game) is an unhappy dwarf. Spending time alone may or may not make a dwarf unhappy, depending on mentality
5. Basic preferences and comfort - drinking preferred booze, eating preferred food, sleeping in a bed, having a table to eat on, not being covered in vomit
6. Labor
7. Aesthetics, entertainment, waterfalls, relative wealth, and meaningful social interaction - Most of the things that players do to make dwarves happy would go here, and they should have little impact on happiness if more important needs aren't met
8. Stuff that really doesn't matter at all - The dwarf who has everything can invent things to worry about, decide that life has no meaning. Nobles make pointless mandates just to feel important.
Adventurous dwarves and soldiers should be relatively immune to worrying about their safety and comfort.