How about dungeon design notes as an in-game object?
I think BLDBLG guy a while ago proposed a city in which each district had a different legal planning system. So like how in modern office buildings the doors and windows and walls and ceiling and whatever all have to be up to spec and there are legal arrangements they have to fill. And the different legal requirements of different nations or jurisdictions are part of what give spaces an individual ‘feel’.
So if there was an ancient culture that built lots of tombs, like the Egyptians. Then they would have favoured historical architects, and a kind of pattern of arranging things. Traps yes, but also how long and far things should be, how deep and which doors, how to arrange rooms in the proper spiritual configuration.
So if you wanted to you could type up a kind of one-page (no need to go crazy) design plan for each culture that built dungeons in your world. You could use these notes when making dungeons for your sandbox and try to follow them and improvise as much as possible within the cultural strictures laid down in the text. Like a real architect would do. Writing within constraints might make you more imaginative and even if they never get the notes they can still work out the logic.
And you could do it in the voice of an ancient forgotten architect-priest addressing future generations. And then those notes could be an actual book hidden in a library or hidden place in that world. So if players rob the library or collection, you just give them your design notes for that book.
Then, though they don’t have the map to any particular dungeon, they understand the logic of all of those kind of dungeons. So they know the treasure room will always be towards the north, at the end of a long hidden passage, and that the number of traps will always be a prime number, and they will always try to take off particular body-parts in a particular sequence. You are looking for the decapitation trap just there. There has to be an upward secret passage from the kings tomb in case his soul comes back and needs to escape.
And then you could have one very ancient culture tomb invaded or re-engineered by a later culture and they constraints would be layered on each other and interact in all kinds of interesting semi-predictable ways.
(in addition to this and in no way related to it. My friend Noisms once wrote a piece about dungeoneers being rentiers because they don’t generate any new wealth, just waste rescources looking for old wealth. It got me thinking about how an economist would account for wealth transmitted between cultures separated by thousands of years. So if the death-obsessed over-culture buries like 50% of their stuff. Then 5000 years later new people invade the ruins and start ‘mining’ them. Does that connect the two economies across the ‘dead’ or inactive intervening years, could you then analyse them as one economy, separated in islands of time?
And. Could there be a genius right-wing economist who is totally theoretically enraged by the ‘dead’ or inactive wealth buried beneath the ground and at the pointlessness of it and the horror of all the money not doing anything, that they would go crazy and start demanding that people start digging it up and recovering it and spending it and using it any way they could just to end the economic illogic of it all. Like if Ayn Rand* (maybe?) or Hayek* (maybe?) was advising an insane king and they were just “we have to dig up ALL the tombs, NOW, all funds must be liquid, both on, and below the earth. No un-owned capital! Anywhere! Ever!”
So then you get the culture of dungeoneers. Grave robbing is now a state-approved and practical job with a hierarchy and bureaucracy and everything)
*Probably neither of those guys would do that but you get the idea.