I think that adding the order "Reserve" to the military scheduler would greatly increase Dwarven versatility.
Currently, a dwarf assigned to a squad, with no active orders, may perform his activated jobs, but is likely to hang out at his barracks and train. Good. We need trained dwarfs.
But we also need dwarfs doing their civilian labors. A "Reserve" dwarf is a member of a squad, can be quickly called up, yet spends his time on non-military tasks. This allows lots of dwarfs to be organized into militias and perform scheduled exercises without having to continually swap dwarfs in and out or have them spend the bulk of their time in barracks.
I see a few drawbacks to keep all dwarfs being pressed into squads.
--All but the most dutiful get a bad thought about "being called away from their jobs", even after they get the weapons skills to not care about being drafted.
--Only rich fortresses can fully equip a large number of reserve squads. The arsenal dwarf privileges full time soldiers (no reserve orders), then called up reserves, and finally inactive reserves. This means he'll spend a lot of time shuffling equipment around.
--Reservists are civilians. They may have nifty uniforms, but only wear them when at least on "no order" duty. So, you can't simply activate them and throw them into the fray -- they need time to equip.
Along with this, I see a useful change to the squad orders screen. When selecting squads to kill/move, it shows if a squad is made of reservists and if they are currently active. So:
a-The Whompers of Might -- a full time squad
b- r-The Unruly Corridors -- the "r" means these currently on their reserve order
c- R-Stirrings of Kelp -- the "R" says this squad has at least one reserve order, but is currently called up and likely equipped.
(You can take this further. "o" for squads on station. "t" for training. Etc.)
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A second, harder to implement, thing I'd like the game to attempt is tracking the danger level of areas. A dwarf is happier to be in a deserted wasteland, than to confront zombie mountain goats, than a skeletal giant eagle, than the same eagle after it has killed. But having a couple great military dwarfs around will get him feeling safe again.
Some critters are more dangerous than others. If bugbats are spotted in an area, they are less a threat than troglodytes, or a Forgotten Beast. The game could remember for a year or two what was in the area, perhaps longer for big threats.
Interactions with critters matter. So, if most of the troglodytes were wiped out by a patrol, dwarfs are less worried working in the vicinity than if the trogs went through unchallenged.
For that matter, if any skilled military dwarfs are patrolling the region, it improves worker morale.
But, it goes both ways. If any dwarfs were killed or wounded, other dwarfs are leery of hanging out there for a while. This also applies to places dwarfs die from collapses, drownings, and other accidents.
So, all these things create a danger level. Depending on how comfortable dwarfs are with risk, they won't want to work in dangerous areas. Some will even refuse to go there. Military officers might use the leadership skill to convince their squads to patrol these regions.
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-Welcome to the Undercaverns, kid. You're looking nervous. I expect Urist McWorrywort has filled your head with all sorts stories. You look out for a few things down here and you'll be fine. There's the heads and the trogs (the hammers smashed a bunch of those last week) and the occasional ogre. But see those blood stains, the guard got them all. We haven't lost anyone since the 1056 massacre. Four good years. We even have the Capt. down here. He killed that Forgotten Beast snake with a single axe blow. (See that green stuff. Don't touch it. Your fingers will rot off.) You're still looking glassy. Let me show you the edges of the patrol burrow and then you can grab a barrel of beer. You'll start learning to gather herbs tomorrow.