So it goes back to what I was saying before: IMHO, the only entity that should have any (ANY, period, at all) control of the world post-generation is exclusively and irrevocably the player. (or the direct result of an (in)ability of the player (creeper going splodey can be attributed to player inability.))
Any mob that mines or crafts removes agency from the player; and in a game where you gain agency by mining and crafting (the two titular mechanics of the game) the removal of them by an NPC creates a lot of problems; the least of which is NPC-griefing.
The OP has made a concession by attempting to limit the effectiveness of this new suggestion; but wishes to maintain that villagers should build, mine, and craft. He is allowed to think so, but I do not support.