Hmm. Will a vampire feed on any species? If so, other than a sleep inducing FB, could unconciousness via dropping wounds be enough to feed them?
I think I remember reading about a vampire who killed an unconscious cat, so I suppose they will feed on unconscious animals, I'm not sure if it makes a difference how they became unconscious.
Personally, If I ever had the luck to get an immortal vampire queen, I'd keep her in an elaborate throne room built specifically for her, preferably out of her favourite material with masterwork statues and engravings, surrounded by her favourite items (but no pets). If I felt like taking a risk I'd probably try to infect her consort (if she has one) using the well of unlife method.
But this all coming from someone who has never (knowingly) had a vampire in their forts, so I have little idea on how to actually make them useful to the fort (except to keep a fort from crumbling til the next migrant wave). If you could knock people unconscious/ put them to sleep then give the queen access to them, then I suppose she could be used to execute people, but I'm sure there are more efficient methods to do so. Besides, I read some where on the forums that vampires don't always drain people completely, but you'll only get an announcement if the feeding kills them, but I'm not sure how true that is.
Overall, good luck with the vampire queen.