At now, we have very unrealistic map, when underground.
We can see through cave walls and map neighbor passes/tunnels, that not connected to our current tunnel system.
The idea is to make mapping in cave more realistic: map only visible part of cave (at least only cave you are in now, not cave behind stone wall)
This will made cave exploring more fun.
You will need visit all cave offshoots, to map it all.
You can mine tunnel and get into new cave system (or neighbor mine shaft ) accidentally.
As addition, Miner or Cave Hermit (or both, but at different degree) can have new feature - Feel Earth - that let him detect nearby tunnels through walls (at radius determined by PER, for example).
Not map new cave (it will be to simple), but have knowledge about it existence in that direction.
P.S.
Yet one cave improvement idea:
Also, it will be great if caves will have natural connections between levels. May be as crack/vertical tunnels that allow go down to next level cave system (if it exist below) without mine hole.
To make things more reallike, use ropes to descend, and it will take some time (> 1 min with hourglass). And build mine hole upon this natural passage will cost less, than standart.
Ascent vertical crack without already mounted from upper level ropes, will need dangerous climb, with high possibility of fall and health damage.
More fun to cave exploration!
(I have some real spelunking experience )
(Sorry for my bad english)