why only for veins? I'd like to see what's above and below. I'd also like damp and warm to penetrate.
I'd like too, but the way we want it requires more changes to the process of mining out a tile. More, as it is now I suspect that every tile would be revealed one z-level below the surface all around the map, which wouldn't be good (I suppose the game tracks everything that is accessible while instancing the map or a newly reached z-level and reveals everything around that tile. Here there would be a need for two different revealing methods - one on loading the map and one on mining that would reveal above and below).
I also thought of something about underground features being discovered while you haven't entered them yet, and it'd require changes too.
But now that I think more, it could work this way : if you mine just one level above a chasm (I mean you haven't breached into it yet), it would reveal only the tiles below your tunnel and show them as empty (miners would've heard it sounded different and understood there was something).
Less changes would let you see whatever is in, more changes would require a new type of tile, with a sort of fog of war.
Also, you could have another degree in damp and warm : the stone directly next to a feature should be extremely wet/hot, almost dropping/melting. There could be an option to remove designation only on "dangerously damp/warm stone", but for more balance and fun in the game it shoudl be decided upon the miner skill.
This way either it works as it does now or you trust your dwarves.
Well, with that last sentence it sounds stupid.
Anyway, let's stop it here now, it's off topic. Someone can copy/paste the quote and start another topic if he/she finds the suggestion relevant.