It's not impossible. I suspect that larger creatures have more blood (although I'm not sure) and thus won't die when fed upon. I wouldn't go with a cave-in system, because it can kill the creature, and I'm suspicious of the idea that unconsciousness due to injury is equivalent to sleeping. I tried briefly to set up a contamination chamber, using evil weather that caused drowsiness, before I realized that there is very little to gain by giving vampires food-- for once, it was extraordinarily difficult to get my dwarves to contaminate my dwarven bathtub. If you found a FB with a non-life-threatening, drowsiness-causing syndrome, and got yourself something big and tame, maybe an adult cave dragon, you might be able to setup a timed feeding chamber. Stationing the vamp there every other month would be a good start; you could use the vamp's own station orders to put him on top of pressure plates that locked the exit until he fed (or at least, until he idly wandered up next to your food source).
But that's based on a lot of conjecture, and the availability of something rare (said FB). The mechanics of it are relatively simple-- the feeding chamber is just a silk farm. Vampire gets patrol burrows orders that puts him on a 1-tile burrow standing on top of a pressure plate that activates a latch that raises a bridge behind him (or something like that); a pressure plate closer to the bait animal raises a bridge, blocking LOS to the FB (assuming the vamp will spook when in feed mode-- it might not be necessary); and a third pressure plate, on the tile adjacent to the bait animal, undoes the latch, allowing the vamp to return to general pop, and lowers the LOS blocker, allowing the FB to put the bait animal to sleep again.
If you happen to be set up for something like this, but can't figure out the mechanics, this is what I'd do:
##########
#######hh^ ->to fortress
#F:bvD^###
####### #
# #
...
# #
#######^#
h^ ## enters here
########
top-down, F is forgotten beast, : is fortification, D is tame cave dragon on restraint v, ^ is pressure plate, h is hatch
Central-top and bottom hatches controlled by a latch, not shown; to get a diagram for a latch, look up memory (computing) on the wiki, and pick whichever suits you. Bottom pressure plate makes the latch open, top central pressure plate makes the latch close. Top right pressure plate linked to adjacent, top-right hatch, prevents entering system from wrong end. Central pressure plate linked to an additional latch-- opens raising bridge next to elephant dragon. Top central pressure plate linked to this latch as well, although it sends a close to this latch, lowering the bridge so the FB can put the elephant dragon back to sleep. Vamp given bimonthly orders to defend a burrow composed solely of the bottom pressure plate.
Just a rough draft-- probably could be optimized significantly, and I haven't given it a careful look-over for bugs. You'd want it out of the way so it doesn't catch idlers-- dwarves that find no reason to approach sleeping cave dragons will get trapped in here, shutting down the system. You probably also want another hatch-plate combo to prevent retrograde motion once feeding is complete.