A while back there was a suggestion of a disease plugin. They would be obtained by getting hit by a certain mob, or something like that, and they wouldn't have any benefits. Just negative effects. Then there might be cures and diseases could be spread by being near someone. I'm not doing the suggestion justice, but it was a really nice and well thought out suggestion thread, and I really would've liked that to be implemented.
On topic, I would like to say something about people (eyebrows) complaining that they can't be a "good vampire". Here's my full opinion on the matter.
The chance of there being a good-hearted vampire is about 1 in 10,000,000 vampires. (at least that's how it SHOULD be, but all the noob vamps are screwing up the ratio -.-) It makes sense for there to INCREDIBLY RARELY be a vampire who attains purity of heart, because there might be some people who are naturally very resistant to mental influence. However, like I said that is INCREDIBLY RARE, or at least should be, and the problem is that all vampires want to be good. This is how it should be, and semi-correct numbers for it too.
On the server, there should be about 70 vampires total (ideally) given the amount of players, and the disease shouldn't be too common. Of those 70,
30 are wretches that live in the undercity, cursed abominations who feed on rats and anything unlucky enough to cross the vampires path.
30 of them live in small vampire bands, or covens, and prey on wandering travelers. These are the vampires that pretend to be humans. Maybe they run a cover business, such as a tavern, and feed on their customers while they sleep.
7 of the vampires are loners, primitive savages who will attack anything with blood.
and 3 of them are good vampires, vigilantes of the night who use their powers to hunt their own kind.
That, in my mind, is a good idea of what the ideal vampire statistics are. I kind of like the idea of a "batman" vampire, who tries to fight the night-crawlers while also having to defend himself from the Regalians. However such a vampire should be incredibly rare, if they even exist.