Returning to the "ideas for how to use money under Baystation code", something I've been running around in my head since last night: it might be nice to have Cargo (or someone) convert cash into Supply Points at a predetermined rate - e.g. 10 credits per supply point (which would put a ballistics crate as costing 600 Cr, for example).
Upsides of this: it adds a 'drain' to the shipboard money pool, which otherwise is stagnant. There's no means of turning credits into 'useful' items barring a sudden, ship-wide mutual agreement to use them. It's much easier just to barter. Using credits to purchase supply points would allow for an actual transaction relationship between the station and NT (and between Cargo and other departments), rather than a "order this for me and I'll owe you one" approach. Potentially, this 'drain' could be balanced out with a 'source' e.g. allowing the sale of plasma to NT for credits, rather than for Supply Points. Or just move from supply points altogether and replace them with cash. I think it also lends itself to RP better ("I can order that for you for 900 Cr by transfer, or if you pay me cash we can forget about the service charge and you can have it for 750 Cr").
Downsides: balancing. Obviously. Currently I think all departmental accounts start with 5000 Cr, and personal accounts start with somewhere in the region of 3000 Cr. This is potentially a huge amount, depending on costs (and I'd expect personal accounts to have much less than department accounts anyway - to another order of magnitude, I would think). Also very significant coding changes (I'm guessing).
I'm the type of person who likes economy simulation games, though, so I could get far too hung up on this.
Fluctuating exchange rates between Supply Points and credits, events triggering/being triggered by purchases and sales (supply shuttle arrivals/departures), etc. Probably way beyond what most people would want/accept.