Unlockable recipes sounds pretty cool actually! I wouldn't mind doing something like that at some point. We're actually also considering revamping crafting as a whole and giving it a tab in the menu instead of having to craft things in the shops.
The idea for the crumbling dungeon sounds very nice, also! You are right, we have all dungeon themes planned out, but who knows if we add a couple more after the game is complete
About a random dungeon, that's also in the "things we can do when the main game is complete"!