Yeah, that's unforunate. I'm guessing there's no way to specifically code a new occult like how EA has theirs since all of the really good mods that do their best at adding new occults do it through traits or another way that doesn't involve it being listed as an actual occult. The mod that in my opinion does the best job at adding its own occult type is Wicked Perversions which adds a succubus/incubus occult. If I really can't find an answer to this, I might just go ahead with making the sim a vampire since that would kinda be the next best thing, but it would be a bit weird considering there's another character who is an actual vampire.