[Lexander]

Uhmmm... it's possible to implement these ideas ... but the vampires have to be powerful if not, theyre not vampires ... what to do is make the game more difficult for them, they not suport the light, therefore the vampires always travel at night and in the day they go in darkness ways, as a city sewers ... the light remove them life gradually and them turn more weak , therefore a vampire attacking in the day is a suicide, but his instinct to survive become more stronger in the day.
They're weak to sacred magic and fire (the sacred magic affects his life and the fire affects the resistance and prevents regeneration), but for kill they you must strike them and they are very agile, have great strength, endurance, an innate talent for black magic and they know how to hide.
Now thinking about the consequences in society, every time you kill a vampire character they drop something, like vampire dust, bones, etc, these things are very valuable to manufacture potions, empowering weapons and to learn powerfull spells... this makes people want to hunt vampires.

Implementing players can be vampires it makes people have more things to do in the game , more possibilities to all.