Become a creature of the night and walk during the sunlight at noon.
It's like putting Lemmy from motorhead on the set of the teletubbies and pretending there is nothing potentially weird or conflicting at all...

While I'm no big vampire fan myself neither, they do have their place in DnD RPG's - with day and night mechanism in place that is - or did you forget about Bodhi in BG2 ?
I remember Bodhi very well indeed. My intention perhaps did not come across in my post; it was not about those creatures not having a place in D*D, it was more about the ramifications of the central character suddenly becoming a Vampire or Werewolf and how that would affect the story and how NPC react to you. It would seem to add rather a lot of work to make it fit the game world.
Ok, I agree, while they do have their place, allowing them as playable characters is possible in theory but indeed would require a lot of resources best spend elsewhere... Unless of course you have Larian's 'staff of unlimited plot armor' and the 'ring of narrative contradictions and plot hole casting' .