Utterly Mad

Also, meanwhile in Kobold Kamp...should I set the IS_METAL token back from only-used-by-arrows materials to the parent stone? Essentially, if I do this I gain the ability to filter stone weapons on the squad menu, in exchange for stone bridges no longer being buildable.

I would put that one to a vote on your mod page on the DF forums. From my point of view though, would kobolds build stone bridges? Personally, I would say maybe. I can see them fashioning stone huts from stacked stones, but if they needed bridges I can only imagine them being rough wooden construction (probably something like a log across the gap) or just tumbling stones/logs/debris into the river until they can walk across. That, or rope bridges. IF they ever got to a point where they needed them.