I have a walkway for my sniper crossbow guys to patrol 1 Z-level above the main entrance. It works very well. The war dogs delay and detect goblins that try to get in and the crossbows shoot them before they get too close. I don't even have to close the main gate. The markdwarfs patrol 4 at a time in a squad of 6. Ambushes are dealt with automatically. All I have to do is reassign a new war dogs to the chains. The biggest pain is the body parts that get severed will go everywhere. They get stuck inside the fortifications and sometimes land on the roof. I floored over the top of the walkway to protect against flyers, since the pathway is connected to the heart of the fort.
the only way to clean these tiles out if to deconstruct the fortification and rebuild it. Someone will come and haul the body parts to the refuse pile. I like to have a clean outside. I claim every single thing and collect refuse from outside. The whole map is walled in except for the entry for wagon traders to get in, which is where my defense is concentrated. I've only lost 6 dwarfs in about 10 years. One of them was a swordmaster. Died of old age, what a shitty way to die for a soldier. Including the sword master, 3 died from only old age. 1 died from a failed mood, 1 got shot through the fortifications by a elite goblin bowman, and one was killed by an ambush because the melee didn't respond quickly enough. I could have set alerts to make the civilian retreat, but I was certain the melee would intercept the goblin first... No, they were sleeping or some crap.
I setup a goblin cage on the surface which turns out to be a ton of fun. It took me 2 sieges to perfect it. I have a 10x10 area of Fortifications. I built a gantry that is 1 Z-level higher for prisoners to get pitted into it.The walkway is fully walled in and hatched so the dwarfs aren't frightened by enemies that are already pitted. I make mark dwarfs patrol around it in a circle with an ammo pile close by. Its super effective archery training. After the first time. No civilians could get near it without being scared. So I built an outer wall layer around it, about 5 spaces offset from the fortifications. As long as I am careful not to pit any ranged or flying enemies it is perfectly safe. I deconstruct the walls to clear out the bodies and get the goblinite. Since it is outside, it never gets stinky with miasma.
With the new animal training changes with the patch, dwarfs can lead prisoners to pit without any chance of the prisoners escaping.I mass pitted about 30 goblins into the cage arena. The dwarfs are walking prisoners halfway across the map with no escapes. I can't say what happens if the dwarf gets scared. So I made sure theres no way the arena is visible from the drop off gantry. It is kinda funny how a weak untrained dwarf can lead a goblin swordmaster to a death pit now. I don't even strip them of weapons or armor. I collect that crap after they have been pin cushioned.
I still need to figure out what to do with the ones that can shoot back. Pitting them off a very tall tower might be a better idea since they wouldn't be safe to use as target dummies.