Having not played previous itterations of Faerie in Sims, but knowing a not-insignificant amount about the folklore (mostly English/European, sadly) IRL, my ideal Faerie pack would have a fairly simple magic structure (maybe 2-3 new interactions each on Mean and Friendly, 4-5 new ones on Mischief, and a handful under a "faerie" category), but a very, very extensive CAS for the Occult form. New body types, new facial features, new skincolors... maybe even new hand and foot shapes. And the human glamour would work more or less like the Alien disguise.
But I'm good on magical sims for a while, and am hoping for Werewolves next... and before 2021.