I've a feeling that paper money might not fit the DF era. Which is not to say that some sort of less formal "promisary note" issue can't be spun by a sufficiently advanced economy, or perhaps (if we can get over the fact that owned objects don't change hands) a hybrid system where the coin economy (when it arises) has a parallel/piggy-back goods exchange system.
Which doesn't stop a pre-economy Dwarf from aquiring any number of silk socks and finding themselves rich, and also has the possible disadvantage (and thus actually in keeping with the DF philosophy of there being a million ways to lose?) of vanity goods speculation or even artifact exchange in order to facilitate the movement of wealth, to then fail miserable when the item is stolen/destroyed. (Or, worse, the 'loss' covered up in ever more virtual valuations and speculation, until the point when some debt needs to be recovered and there is nothing to back up the supposed wealth of a certain individual, toppling the whole system in a frenzy of economic implosion.)
No, I don't think the above paragraph is easily workable. I'd stick to using coins
if necessary, but in the expectation that purses of some kind could be added to simplify the hauling of "ready money", but backed up by the credit system that is currently 'ethereal' in nature, but perhaps transferable to actual 'books' that the accountant/treasurer assigned-noble does actually maintain. (If you feel that the potential (and/or deliberate) loss of those books would be something you'd want to risk(/exploit)... At the moment it seems to be a "collective consciousness" knowledge of the wealth of all non-noble residents. Perfect and yet intangilble. Which is why I suppose a lot of people turn the economy off, and settle back into the more feudal supply-and-demand non-economy that exists in the initial settlement.
The opportunity to guide which of several (suitable in-character) economic models/mixture of models get used would seem interesting. But would that immediately arrive (or even eventually lead up to?) a paper economy? Unless done specifically to annoy the elves, given the current tendency for one entire tree to become a log to become a single 'block' and then to become a single wooden earring (at least in the hands of the inexperienced), so it seems natural that one entire tree would eventually become one (or maybe three/nine, I suppose) treasury note of some kind.
(Back to game mechanics, if we currently have problems with coin haulage, in leiu of a 'purse' mechanism, then we'd have similar problems with paper haulage, in leiu of a 'wallet' of some kind. Unless you go down the lines of having multiple magnitudes of value to specifically handle this issue, but then you'd have to deal with 'change', as well.)