I like werewolves especially as a foil to vampires. It always feels weird to me to have one and not the other. I'd want all supernaturals to have a perk tree like vampires with stuff suited to them.
Werewolves would have a transformation and would need body hair assets and preferably a full moon system. In 3, they hunted collectables, walked on all fours, and bit people to change them. I'd like the wolf that can do the first bite to return from 2.
Fairies were granted trick magic, auras, wings, and fairy houses in three. They were not my absolute favorite, but they were always fun and would give me more supernatural variety.