Just think if the miners dug tunnels right under your defensives walls, making a neat little passage for enemies to funnel through. The enemies using my own mining networks underneath me has been a fear since we started discussing the ability to change terrain in Stonehearth.
One idea for less ‘overseen’ miners that’s been thrown around was the concept of “nodes” that produce minerals ( @BanditDragoon ) . Perhaps these are a sort of magical vein of ore that gradually replenishes itself overtime for a steady trickle of minerals. I wouldn’t mind seeing some version of this alongside normal mining, since it would make having a main, established city a little easier to maintain–otherwise, you have to continuously set up new outposts for mining just to get a little more iron, coal, and other basic minerals. To get a lot, you’ll of course need to venture out, but nodes could give enough just to keep a basic output of materials and goods going.