So we have a dynamite or pick axes called "stone removal", and a tomb called Siege Camp whose entrance is buried in rubbles.... lol
Either they have a reward system for dynamites of limited number a day, with which you gain access to the tomb to fight for extra goods.
But the problem is that military 'racks are huge. Is it worth it to build them instead of goods buildings? Sure, the merchant in Japan works great, but he doesn't take space or resources from the settlements. It's hard to keep the balance from design.
Or it's more like GE, you will have a seiral of passes after open the tomb, with each pass you can either fight or nego. Wonder if you've found any underground map background images in the files?