Okay I think it's been stated in this thread earlier. For Sieges (larger ones) in which the attackers have tried to breach walls and such
they would try to tunnel in. This doesn't meen 8 zlevels down or try for "from the bottom up". So they would try to do just enough to
get under Outer walls or under the river. Allow them to catch the idea of damp stone=bad, warm stone=death. Logically you would want
to get as close as possible and dig as little as possible trying to break in. Plus like Goblin Trolls, have them bring 5 diggers (note NOT
miners as that would imply greater skill) for a 50+ size siege. This would give reason once better squad control is adapted and possible if
the player could set ambushers of their own (dwarves that lay in wait hidden while waiting for enemies to pass by and let then let the
axe fall). Also equipment should be taken into account. Steel items seem to be used only by dwarves so they could with them dig
through any stone (adamantite would take MORE time then others but is possible) and an Adamantine pick would slice through the earth
like a knife through butter. So you could line your rooms with variant materials to slow or downright stop digging. When a digger runs
into a wall what does he do? Send the Trolls/battering rams/Trents in to tear them down. And Kobolds? well lets say one makes it deep
into your fort and learns of where the Treasury is and makes it out ALIVE well using the stolen goodies= how bad Kobolds get let's say
they steal a LOT and know where this room is they try to dig there. Once Hidden doors and secret passages are used they make thier
own... Right to your treasury of adamantite spittoons. Of course if they don't have Steel pickaxes that would limit how deep they could
go, but if they have successfully procured some you might get an open season! Plus once Siegers have already started using a tunnel
they try to add to that one until it becomes completely useless (you use a flood trap on it once they know not to use it ever again. Plus
they might want to protect these tunnels so for smarter races like Humans they might set up their OWN traps to make you think twice
about following them down their tunnels giving your engineers a new task: disable traps. Same goes for the enemy (smarter races at
least) for them being able to dismantle your traps. Siegers using Mantlets and such might be an interesting add to. Think you can abuse
Crossbow users to your hearts content? how about a small protective wall coming down the field/hall that is defending a small group of
enemies until they can solve the dwarven crossbow problems.... OH THE POSSIBILITIES!!!!