When I see a cavern full of webs, I cannot resist, and I ignore the safer options of digging out rooms for cave spiders or making a GCS farm.
I focus on mass-collection of webs, then dye them later. Here is what usually happens:
- turn off the auto-collect and auto-loom orders, set up 4 looms below for low-skill weaver training.
- put 10 new weavers in an bone/copper armored squad, with barracks to do combat drills. When not activated as military dwarfs, these dwarfs have the good odds to take down a GCS by themselves without being webbed, because of their training and importantly because GCS only start webbing when confronted by active military. So they train when not collecting and this helps them survive in the caverns against dangers.
- The gate is opened, some axedwarfs are sent to murder local wildlife, the four looms are set to collect-webs-repeat. When the webs run out or a real danger arrives, cancel the looms, recall the weavers, and lock the gate.
- To bring the hundreds of silk threads upstairs, no minecarts. Minecarts would involve one job per thread at the pickup site, that is not efficient. Use a 1-or-2-tile stockpile for silk threads with 1 bin (the bin is stationary once assigned to the stockpile, even if empty, so the bin will not break your fort if you prefer to not use them). If you have a lot of jobless dwarfs, they will carry up 5 or 10 threads upstairs per job because the Put Item In Bin job adds threads to the job while the dwarf is walking downstairs. If you have few jobless dwarfs, the Put Item in Bin job will keep adding new threads to the job and the dwarf eventually assigned to the job may carry hundreds of threads upstairs in one haul. Once the webs are upstairs, set the stockpile to only-accept-from-links (this will stop it from collecting newly dyed threads and stops any bin-locked job-cancels). Ignore the system until you run out of undyed thread, then check if the caverns have enough new webs for another dwarf-mob-ravages-the-landscape event.