Isn't the trade-off the fact that these Chinese owned mines become exclusive suppliers and the "captured market" effect takes them out of the world supply equation?

Having become a sole supplier to China, they effectively take themselves off the nickel markets as a world supplier, which in turn tightens supply to the rest of the world. To me that may balance the effect of taking away the demand side created by chinese buying.

Just my thoughts

Is the balance of world demand enough to carry on as usual with the remaining nickel supply? Free markets will always eventually find balance.