So I really enjoy ruin structure generator mods but I've never seen something like this before and I would love to play with a mod like this - unfortunately I've never been able to make one.
The main idea is a mod that generates some kind of moss that overgrows blocks that have been placed e.g. 1000 in-game days ago. These blocks would have different phases depending on the time they have been in the same place and eventually there would be grass and flowers growing on them. And the player would have to move the block or use shears in order to remove the moss.
Another idea is to have small things like ruined chariots generated on the ground which have already been overgrown by the nature. I think small things like these would make the adventuring side of the game a little more exciting.