I personally see no benefit - and clear downsides - to keeping 500-unit stacks. What downsides?
1. If they get split up, it is possible to get terrible item spam. This makes gameplay more tedious and hastens death-by-CPU.
2. If a way to split them up (say by firing them) is used, the individual coins or ammo can be melted to get a LOT more metal then making the stack cost. I personally find this to be almost unacceptable, as it's making gold out of thin air.
Basically, coins are hard-coded. There's SO MUCH we simply cannot do with them (at least, not by making edits to the text files).
I also strongly recommend we not use ammunition as a currency. No in-genre rationale. Not enough control over weight, value, or cost to make. But, more than anything else, you get CRAZY high melt returns from a stack of 500 ammo! See
http://dwarffortresswiki.org/index.php/DF2014:Melt_item.
Objects of TYPE_TOOL avoid all of these problems - that's why I used them. Unless DF has changed the rules on me, the SIZE and MATERIAL_SIZE given in my previous post should yield consistent, understandable weights, costs in bars to make, and melt yields. All of this is critical for any coinage based on precious metal value.
In short: I still think that we're faced with a choice of coins or named tools, and I lean towards the latter.
Because of these (and a few other) arguments, I re-cast all of the MDF V6 trade and raid reactions. A couple of examples follow.
[REACTION:BUY_ANVIL]
[NAME:Buy anvil for 1 tyran]
[BUILDING:CARAVAN_GENERAL_ORC:CUSTOM_A]
[REAGENT:coins:1:TOOL:COIN_TYRANS:INORGANIC:GOLD] 1 purse of tyrans
[PRODUCT:100:1:ANVIL:NO_SUBTYPE:INORGANIC:IRON]
[SKILL:POTTERY] #scribe
[REACTION:BUY_ANTHRACITE]
[NAME:Buy 6 anthracite for 1 tyran]
[BUILDING:CARAVAN_GENERAL_ORC:CUSTOM_SHIFT_A]
[REAGENT:coins:1:TOOL:COIN_TYRANS:INORGANIC:GOLD] 1 purse of tyrans
[PRODUCT:100:6:BOULDER:NO_SUBTYPE:INORGANIC:ANTHRACITE]
[SKILL:POTTERY] #scribe
The changes I made were to:
1. Use items of type TOOL.
2. Revalue based on the new material values.
3. Make trade prices internally consistent, based on a common understanding of what factors drive merchant profit margin.
4. Handle additions and deletions made elsewhere in the Wonderwork mod.