I usually put my Ger on my Ovoo to get the “Improved” tech upgrades. I might as well be doing something useful with it while it’s there and get my upgrade faster. Mongol villagers should be able to mine from their Ovoo. Malians can mine from their Pit Mine.
Mongols wouldn’t get any advantage from it. We’re basically pulling man power away from other resource-gathering, so it would all balance out.