Currently weapon traps are very powerful. They reset by themselves, can be placed anywhere, take very little room, have a low chance of jamming, can hold up to 10 weapons in a single square and are very easy to design. There's very little that can survive an over saturated trap corridor or even a lightly armed one. Most senior players don't use them at all thanks to them trivializing the game very quickly
What I'd like to suggest would make traps much harder to design, space consuming and generally less effective while keeping them useful and easy to rebalance by the players themselves
1. Make weapon traps 3x1 squares and rotatable. Enemies standing on any one of these squares would trigger the trap instantly and deal damage to all three tiles when applicable
2. Reduce the number of weapons. Limit weapons by size, for instance 2 large weapons and 3 small ones. The large weapons would hit all 3 squares while the small ones would hit only one each. Large weapons would generally of the twohanded variety, for instance Mauls, Giant Axe Blades, Spiked Balls and the like while the rest count as small. Placing blunt large weapons in the trap would let the player choose which direction enemies are knocked if at all
3. Make traps require walls 1 z-level below and above them. Not just floors, solid walls, natural or otherwise. The weapons come from somewhere. This would limit their placement. Small weapons would require squares below and large ones would require them above. This would allow players place traps outside but at reduced effectiveness if they don't build a sort of gate structure housing the large weapons
4. Traps no longer reset automatically. They have to be reset by hand if they have no power source. Individual traps would have a setting to turn off the manual reset.
Power could be rigged via animal/slave
(ethics raws) power building below or above the trap into the trap's middle tile. I'm not sure if axles are a good idea for this, they'd make traps exceedingly difficult to design and unsightly. Power could simply be transferred through stone or walls 2 z-levels above and below the crank from the central square. A large animal would be required to turn it so no kitten power. Replacing the animal would require deconstructing the building
If the trap is replaced by an axle or a millstone, it gets turned with the power that is transferred through the wall from the animal crank. This serves to give the building a use beyond arming traps from safety
A basic trap design:The animal crank would basically act like a screw pump. An animal is built into it and start and stop settings call a dwarf with animal handling enabled to stand in it (this labor would not have skill levels). Any time power is required (ie a trap is sprung, wheat is milled) the dwarf drives the animal around the central square and generates it. Animals might get exhausted after a while of continuous use, disabling the system. The building would have two settings, constant use and one where power is supplied only whenever needed. While power is being provided for the purposes of milling or reloading, any traps connected to the machine would not fire as the reload mechanism being activated would effectively jam any already loaded traps for the time being. Any dwarves doing milling would treat the millstone as if constantly powered but the job would not start if no power is actually present. The dwarf would instead simply stand there waiting
Resetting a trap would take power for a number of steps. The amount of steps required would be in the raws, letting players effectively choose how often their weapon traps can be sprung from safety. Long reload time setting would make traps take out much fewer invaders
5. Jamming. Default chance per activation could be 20% which could be raised all the way to 100. Jammed traps would need to be cleaned before they can be reloaded again
Enemies could of course drive animals and slaves into the traps they know off in an effort to jam them but advanced siege tactics such as that are best left for other threads
Eventually animals will need to eat so this in mind, animal caretakers could bring them food and water much like health care enabled dwarves do to injured dwarves
A pain in the ass to code to be sure but I think it'd make traps worth using yet limit their power quite a bit. Players wanting automatically reloading weapon traps would need to sacrifice space for it whereas people who risk their engineers could cram 2 more traps into the same space. I imagine a quick orders menu item to temporarily disable reloading and cleaning would be handy too, as is dwarves have a nasty habit of running into an enemy siege in an effort to clean traps they just sprung
Any other ideas, feel free to add