I don't think we have to get involved in mining directly. I think that the merchant guild should limit itself to trade and the distribution of financial instruments, including loans and insurances. Money printing machines are really outside the scope of our mandate. The mage's guild is involved in that because it's a luck based operation.
If there's something we should do in response to the mage guild thing, it's to establish a payment plan where we sponsor somebody to mine using the mage's guild system, and take a portion of the profits whenever they succeed. Obviously we'd balance this to earn us a profit. We're bankers and merchants, not magic workers.
In the OP of the OOC thread, roseheart mentions that developing items and equipment (including mechanical ones) is also a responsibility of the Merchant Guild, because
somebody has to do that. Perhaps you don't want to make mining machines -- fine (we'll put that to a vote), but otherwise we still need to create some kind of physical objects, not just financial services.
As for our mining machine, I think we should make it so that the probabilities of getting a small chunk, average chunk, etc. are the same as manual mining, but make the machine mine about 12% less, so the average income is 7.67 per turn instead of 8.75. We get a quarter (about 1.92) and the user gets 5.75. This model is assuming that users valuate their ability to do an action at any turn at about 2 gold; we can change it later if we find out that's not quite accurate. What do you think?
We really need a guildmaster so we can get this running -- we need to appoint a Bookkeeper at least, but I can't create that position without being guildmaster.