You mentioned that the amount of enemies, and their blood reserves, in the game are finite.
So I came up with another argument for having vampires using a coffin. Once a vampire is in the coffin his 'hunger-meter' stops. This way you can go to a town, put your vampire on a coffin and the rest of the party can go shopping, ponder over some crafting, read the journal and other town-stuff, without worrying that your vampire will soon be a ticking starve-bomb.
That's actually a really great idea. Perhaps I could also make a way to enthrall someone, to gain a party member with "mini" vampire bonuses.
It's worth mentioning that townspeople/civilians are potential blood sources too. I could tinker with making bite possible from stealth, or maybe it applies a "dazed" debuff that gives you time to get away before they go hostile. Or, using an unnatural charm ability to increase their attitude to friendly, and taking a bite then would prevent combat until you've drank too much.
