I found this post because I came to an idea of molds and sand casting too.
For example currently it's a sort of magic how a hearthling makes an anvil. AFAIK in a real life we would need a mold, a sand and a box. And, of course, a metal in a liquid form. And in the game we could imitate this process somehow with sand, wood (for box), wood again (for mold) and melted by some process metal. It would be interesting IMO and also q of an anvil for example would be affected by many ingridients and not only metal q. We could extend this principle to other metal stuff - cauldrons, tools etc. Or use it just for big constructions.
Thx for your attention