Given that many Native American groups, including the Lakota, consider Black Hills a sacred site. I wonder if a slight adaptation of the concept of Mountain Monastery could be simply applied to the Lakota.
Introduce a building named “Sacred Site” or other suitable name to replace the current Tribal Marketplace. It can be built on top of mines which are considered sacred hills, and Villagers can be tasked on top of it.
Visually, Villagers will have some spiritual or religious activities on Sacred Sites, such as astrology or playing musical instruments. In fact, Sacred Sites have a trickle of XP, and Villagers on there can boost the trickle substantially. In addition, players can switch the exchange rate so that some (or even all) of the XP trickled by Sacred Sites can be converted into coins.
If Sacred Sites will consume the content of mines, the Villager should be able to boost largely until the mine is “depleted”. In this case, the building will not disappear, similar to Mountain Monastery. At the time, Villagers can still continue to work there, but the trickle will be meager.
If Sacred Sites won’t consume the content of mines, it would be somewhat similar to Shrines, occupying the resource source and providing a trickle. It’s just that the gatherers there are Villagers rather than wild animals, so the benefits of each gatherer are far more than each animal of Shrine.
The Gunslinger is the upgrade of Pistolero, and the Lakota can already train it at Embassies and upgrade it with the card.
I would like a new card named “Gold Rush” which makes outlaws stronger and allows the Lakota train outlaws with less population and cost. Maybe it will need a minus effect to balance, like Villagers and buildings -8% HP. However, I don’t think it should affect the Mortars. There is already Advanced Captured Mortars for them.