I had a non-vampire sim pass out right in front of the movie cineplex.  Just fell down on the sidewalk and started sleeping.  My sim and the person she was talking with both stopped talking to turn and stare at the sleeping sim as if to say "WTF, over?"

And somebody, please, make a proper coffin for vampires to sleep in. The current vampire bed is semi-interesting only until you make the joke from the first Ghostbusters movies, "She's interesting because she sleeps above the covers.  FOUR FEET above the covers." After that, you've pretty much got nothing.

I'm sure there's a host of things to consider in implementing something like this.  Perhaps the ability, for player-controlleed vampires at least, to only fill themselves up to 25% or 50% thirst to lessen the risk of killing.  I like the idea of a motive check under "read mind" too. And you'd probably need to bunch of tunings for NPC vampires to keep them from systematically killing/turning the entire population of a town. Perhaps not letting them drain anyone below 25% hunger.  Or maybe giving them a small random chance of killing/turning while feeding.

Perhaps a mechanic were a vampire feeding off of another sim replenishes his thrist motive by draining the target sims hunger motive by an equal amount?  In which case an especially thirsty vampire might end up killing his meal (and possibly turning them as well) if they're not careful.