I don't think you can be a vampire and a witch at the same time but it would be cool if witches run in Hayley's bloodline then the baby could be a witch and a werewolf. Werewolf may be a curse but the species was always more natural tha vampires, they aren't immortal after all. I actual doubt that this baby will have anything to do with vampires considering its the werewolf gene in Klaus that made him able to pregnate Hayley so technically it shouldn't have any vampire traits at all. On the other hand it's possible that even if either a witch or vampire trait won't be find it won't be a normal werewolf.
Klaus is a vampire and a werewolf. Witches aren't immortal and aren't against nature. I was speaking about witch werewolf or witch vampire. Nature won't let you become part witch/vampire or witch/werewolf. It is a conflict of interest if you are a servant of nature but nature fights against you. Then there will be a conflict of interest with your vampire or werewolf side with your witch side.
What do you think?