Pleasepleaseplease allow laying stone in caves. It isnt necessary to build something there, but pavement for being able to pull a cart would be so great.
Reason is, some mines (mine for example) are so deep inside caves it takes ages to mine in them. I have to run ~3 minutes per load from caveentrance to mineentrance, a cart would at least allow me to take 5x the load i can travel with now.