So there’s about a square meter of space per tile, right? And the way pits currently work is that you’re able have separate pits right next to each other, but with the amount of dirt they’d have between them as a wall in order to make the happen it’s hard to think that thin little wall is going to stand the test of time or rain, much less the forces involved in the digging of a pit. Sooner or later you’re going to have a single rectangular pit instead of two circular ones whether you like it or not.
So I propose this: Like how water currently is, a “Pit” type tile should behave in a similar manner and all tiles of this type should be connected. A shallow pit wouldn’t incur much aside from a movement penalty, but move from normal terrain to a deep pit and you’re in for a bit of a fall unless you can mitigate it like putting down a ladder or rope first, or using a shallow pit before going into a deep pit, or by having certain traits or CBMs
It goes without saying that moving from deep pit to deep pit if it were to be changed like this shouldn’t slow you down or hurt you due to it all being one big hole, so if you actually wanted to have successive pit traps to damage the horde you’ve lured you’re going to have to separate them by a tile each. Using a plank to cross it shouldn’t work either unless two normal terrain tiles are next to the tile being planked. Additionally, being in a deep pit tile should block sight out of it except for the edge, and anything outside of it shoulldn’t be able to see much into it unless it stood at the edge(unless you plan to use some sort of pythagorian formula to calculate how big the pit must be in order to see more than one tile out of it if you were standing in the middle).