Might be more interesting with a way to 'dig deeper' on old ores to re-open.
Or even just dividing workers among the ores.
Maybe an 'Improved Purity' upgrade for better ore prices?
This may be a far future thing, but what about base improvements? Maybe a shrine that could improve heal speed? Or a merchant stall that improves how often they show up?
 "Mine Upgrade"){kind=icon}
 "50 years (graphical)"){kind=icon}
 "Idle Raiders"){kind=icon}
 "Woodclicker"){kind=icon}
Oh, that's not a far future thing. We will release a big content update next week, and the first couple of base building things will be in it.