Cervator: Agree, although the space where resources can be found is heavily limited then.It might have some advantages if we don't want players tunneling across the entire map. Another possibility is leaving the world very "thin" to not leave a huge underworld to tunnel through. Overworld is better for this sort of thing.
What do you think of playing cards as resources, which are produced by the playing card minerals constantly. You can attach tools to said blocks to get better cards (hey, there are enough of them in a deck of cards ). A simple blueprint mechanism could be to just align different cards on a book page as recipe to craft weapons/ summon some slaves/ get building blocks from a mason/...