Buying and selling is fun. Being able to hoard stuff is fun. Being given stuff as a reward is fun. I've been thinking more about the economic side of things. Mainly I've been thinking about things that you use lots of and are likely to have stockpiled. Stone, wood and metal for example would be the goods used to expand your guild house. Meat, fish, spices, wine and beer would be consumed by your guild members.
I want a tiered system, where goods can come in three flavours; common, exotic and rare. Not coincidentally these classifications work as universal prefixes for any of the goods I've mentioned so far. Common goods would be the default and exotic goods useful for the kind of stuff you'd like to migrate to as your guild improves. Rare goods would be very valuable - a quantity of rare meats, for example, would be an appropriately valuable reward for a mission - the kind of thing that you always want but can't necessarily afford.
Because I don't want common goods to be irrelevant to higher-tier players and I want exotic goods to remain feeling exotic, I'd make it so quantities of common goods are always required for anything of that type, but higher-level stuff might also require exotic or rare goods. So a basic guild hall might need 10 common wood and 10 common stone, but a mid-level hall might need 10 common wood, 10 common stone, 5 exotic wood and 5 exotic stone. Numbers pulled out of my ass.
It would be really easy to add extra levels of quality over or parallel to rare, but they'd probably be special cases. For example, "mysterious" meat that might be used to make the best meals of the game or be totally useless - with no way of knowing until you try. I also wonder whether there should be a staple food category for things like bread, milk, cheese and eggs that isn't interesting to be detailed. You just stock X quantity of "staples" to pad out your guild members' diet.
I'd like to encourage a lot of trading and speculation on these kind of goods as their relative value changes week to week, which means a limited supply. I've vague notions of players having an income of X units of resource Y per day based on their location, and also with access to a trader who will sell and buy goods for variable prices. But those are still vague ideas.
To go back to food, individual characters could have a preference for meat over fish, wine over beer or vice-versa and get an increased benefit from foods of that type. They might also specifically love or hate spiced food. That could be interesting, or boring.
I think food is going to be one of the major expenses for supporting a large guild. A money sink to help mitigate mudflation. But I don't want it to just be a meaningless expense.
Characters have a "stamina" value which is boosted by eating high-quality food. Stamina is like a pool of healing that is automatically depleted by characters to remove damage in between encounters. High stamina doesn't make individual encounters any easier, but it gives you more margin for error for the mission as a whole. In this way high quality food and drink can be a tactical decision before a difficult job.
The mechanic probably needs a little embelishment and tweaking - maybe making stamina level determine a regen rate rather than actually depleting to heal - but I like the basic idea.