I know the Great Toad plans on implementing a system whereby goblins don't wanna walk down the same trap filled corridor that just automatically turned the leader of their squad into finely diced bits, but, in lieu of or in addition to that, I thought why not add in a simple way of interfacing items and kill locations with the pathfinding system.
That is: If there is a goblin corpse sitting on a tile, the pathfinding algorithm for goblins treats that tile as costing an extra 9 points to move over or something, and as, over time, goblins (or humans, or elves) bring back reports of your specific fort to their civilisation, pathfinding costs where goblins die slowly accumulate. So you could have where, if a goblin makes it out of a siege and off of your map alive, he spreads his rumours/reports to his superiors on the deadly layout of your fortress, and, as a result, the pathfinding cost for every tile on which a goblin died increases by one. Over time this accumulates until the +large, serrated adamantine disk+ filled trap hallway no longer seems a better route to the trade depot than the three tile wide wagon route that winds around the mountain and back.
It fits in with the narrative (i.e. rumours of a place/hall/bridge/gate that is death to goblins/humans/elves slowly builds up), and it wouldn't cost any in FPS, as we can already assign our own pathing costs to tiles with the designate tool, with no cost to FPS (in fact, if done right, it actually increases your FPS).
Also, we already know that the engine can deal with different pathing costs for different tiles for different creatures because the traffic designations you the player applies only affects the dwarves and not members of other civs.
Thoughts? I personally don't think this would be too difficult to implement, and given that you generally don't have hundreds of goblins dying in the same instant, I don't think running an extra line or three of code on a goblin's death would be too taxing on the hardware.