We currently get warnings when we're about to dig into magma or water of the dwarves hitting warm or damp stone. While a cavern isn't as immediately dangerous to dig into as magma or water, it still would be nice if there was a similar warning when I get near an unexplored tile of open space, lest I expose my fort to cave creatures and forgotten beasts.
I must admit I don't know much about real-world digging and mining. Would a miner be able to tell by the sound of the pick hitting the rock whether he was close to digging into an open space? If so, maybe there could be some sort of warning of the dwarves hitting hollow-sounding rock.
No. Instead all such warnings including being warned about warm/damp stone should be removed, or at least moved to an init option that's off by default. Wussies can turn it on. The old 2D version didn't have any such warning, and it was Fun. Nothing like the risk of a flash-flood to keep you on your toes.
/data/init/announcements. You already have your init option, just remove D_D and P, and there you go.
In fairness, this isn't quite the same. The dwarves will still remove the designation - which can be even more frustrating when they cancel their ordered digging job with no warning or explanation.
I don't agree that it should be off by default, given the stiffer consequences(everything below that point
will permanently flood, instead of maybe temporarily doing so), and it makes some degree of sense that the dwarves could tell something was amiss before they broke into such a feature. It's also much easier to guard against flooding when you know roughly where it will happen, than to build every single new mineshaft with it in mind - and I mean in this sense the willpower of going slowly where you need to be concerned, instead of forging ahead.
Perhaps there could be a range of options for such things. On the one hand, does the player get the warning, either told that the rock is damp/warm/"thin"(or whatever) when examining the tile, or by a flashing indicator when designating? On the other, do the dwarves stop: reliably, based on mining, not at all? The people who most benefit from the warning are the ones that might still be daunted by the complexity of the game, which is why I don't think it should be off by default(negotiable, though - invaders and economy are on by default, and the former especially can be hard for new players to deal with while part of the expected challenge for veterans) - but having the option to disable that function seems entirely reasonable to me. As for the flash-flooding, that may return when watercourses aren't an automatic and perpetual 7/7 in every case. Smaller waterways may be shallower, and there may be occasional flooding, seasonally (especially for the ones that lead up into the mountains - spring thaws in the foothills, anyone?) or randomly - but that will need an overhaul of the fluid system. Right now, even if it could be done, it would bring many players' machines to their knees.
I agree that more, smaller caverns would be more like how I envisioned the caverns in the first place, more realistic(not that I want to automatically lose them entirely just because "in the real world, there aren't caves everywhere"), and would make them probably more fun. If the creatures below can be made to just plain ignore any region they don't have a path to, only checking on tile passability changes if this is no longer the case, that might(?) help with the FPS issues, especially with the creatures that really want to attack the fortress rather than doing so at opportunity or defending their territory. On the other hand, there's a valid point that any but the clumsiest miner should be able to tell they've breached a wall, peek through the hole, and seal it back up without needing to construct a full-on wall. (Soil perhaps not so much - if you disturb it to that point, it makes sense that soft materials would crumble away.)
But if there was something deliberately sealed down there, it might notice even that small breach, and might not give them the time to do so. Yes, it makes digging up the caverns more hazardous to put such "cells" around - the things that can be thus entombed and survive to ~greet~ your dwarves might not always be colossi, but they're probably not biological in the normal sense, and probably going to be active and instantly hostile. But it
is Fun in the spirit of DF. On the other hand, if you're going to put that much risk into the caverns(and not have it be a tuneable option in the worldgen) would make it all the more punishing to then not give dwarves a way to know that they're about to hit them.
It would make insta-cavern challenges a matter of luck. Do you hit a sprawling mostly-empty cavern with space to settle in and plentiful resources? Or do you hit a bare stone cell containing a monstrosity that will slaughter your starting seven without the slightest difficulty? Even more than forbidden beast attacks, it would be a luck factor that players simply cannot prepare for within the scope of that challenge.