Fairly sure Fane is human undead only.
If you look at the button where you change between races and origins, Its clear that you can only play Fane as a human undead.
To be honest I feel you gain more when playing as a non-origin story, simply because you see more dialogue from that character, and you can befriend them, too. Doesn't stop you from doing their quests, and you can switch between them.
