This is a great simple thing for you to do and FUN for us! This will require very little programming! I know from other posts that Devs want to limit stone use. Limit it in trading, on the map, and make walls more expensive. This is fine. It is worth more than gold. BUT a trickle of stone in the late game is FUN. Tithe barns is very popular if you happen to have a relic. The idea of the Mansa Quarry is fantastic. [Note I actually never build it, because I love the tollbooths so much.]
The concept is a mix of the Mansa Quarry and the Sultanhani Trade Network. Basically everyone gets a mansa quarry, after you research an “underground quarry” in Imperial. BUT you don’t have to give us PASSIVE stone if you don’t want to. I imagine this would defeat your objective of limiting stone. Besides, that is the Mansa’s specialty.
Rather, like the Ottoman Sultanhani Trade Network, we could garrison vills in it. Just like 1-3 or 1-6. So it takes up pop. AND they don’t even have to mine at a good rate (just like the bad rate at the sultanhani market). It could be inefficient like the 28. Even for 15 stone per minute per vill (5 vills x15 = 75 stone/min like Mansa) and I would still build it every time! Though a good rate and passive stone is fine with me too, even better.
This would not break the game but would be FUN. The Mansa quarry is passive and 75 stone/min doesn’t break the game. And the guild hall is way more stone. Come on, this would be simple to make on your end and FUN. Just take the Sultahani, pop a skin on it like a cave entrance, change the resource to stone from gold, put vills instead of traders in it, give it too all civs and research it at university or mining camps.
Rocks!!! For repairing all my broken walls. There must be rocks underground. Thanks!