So I've got it all running.
(I had a lot of trouble with it. Good thing the FB doesn't need path, because my system, umm, didn't work. Guess they don't need hands to open tightly closed hatch covers. Anyway, managed to recover with only two casualties, and did a slight redesign since I didn't need path.)
The vampire has hauling and weaving enabled. When he picks up a gather thread job, he travels along the south passage (because if he goes north, he'll lose path). Along the way, he trips a pressure plate connected to a goblin-based memory cell (not pictured) that raises the bridge, blocking LOS to the FB. He goes in, gets in silk, and returns to the farm via the north passage (because, again, he'll lose path if he tries to return via the south passage). Along the way, he returns the goblin memory to its original configuration, and the bridge goes down, and the room refills with silk.
When he decides to haul, he goes to the stockpile square, but finds himself without path-- he drops his silk on a hatch cover, and travels underneath the structure (because hatch/plate combos control the direction of his movement along this path as well). Along the way, he trips the hatch he dropped the silk on, and the silk drops onto a bridge underneath the hatch (not pictured). Next time he goes to collect silk, the bridge will open, and the silk will drop out of the system, to be collected by dwarves.
The entire system is self-contained; there is never a time when any creature has path to the vampire, the goblin bait, or the forgotten beast, and all are protected by walls and building-destroyer-proof buildings. I have a central emergency area, with anvil, pick, and axe, as well as levers to manually raise the bridge or allow bypass of the directional passages, just in case I need it. The only point of weakness right now is the goblin memory cell, which I may sometime replace with a walled-in water-logic system. The vampire, the goblin, and the forgotten beast are all immortal-- the only risk is that the vampire somehow goes bonkers, which, since he's utterly alone and friendless, I don't see happening. TLDR: It will drop silk cloth until Armageddon, without any oversight necessary.
PS: Oh hey, my vampire is webimmune. That's interesting.