i've had so many of these working on imsims. my first was the guards in my stealth game who could hear each other's footsteps and if they didn't already know roughly where the other guy was they would investigate each other and be surprised to see each other. in first person this looks like nothing
thinking about this again today, and not even in the context of procgen. The thing about systems design is that it's so easy to get excited about making little sandboxes for yourself that you forget the player needs insight into it, lest it simply appear the same as complete randomness.