Occult Ideas
I love occults, and I know there's some buzz around new occults, but I'd like to see some updates to mermaids and aliens as well if you're going to update old packs.
Skill tree for mermaids: Add better weather control and more mermaid "spells" and better hydration control as you level up. Maybe faster fitness or charisma gains as optional perks? An option to switch swimming style on command so they can snorkel if required to by the Conservationist career? Perhaps weaknesses where they get homesick for the ocean or either don't want to eat fish or want to eat basically nothing but fish.
Skill tree for aliens: I don't know, more mind powers, better skill gains, better disguises? Perhaps optional weaknesses where their disguise is worse, or where they're socially awkward because they don't understand human ways.
(I adore both aliens and mermaids, especially mermaids, and would love to see them get more love.)
For new occults:
Werewolves: A skill tree where they can learn to either control their transformations or a weakness where they're less controlled in exchange for more ferocious powers. Perhaps one of the high-level perks could be to disguise self as a different animal (cat, dog, llama... werellama, anyone?). Trying to balance feral instincts vs. living a normal life. Another weakness could be guilt about attacks, and a perk could be choosing to attack or not attack.
Fairies: Perhaps great at nature and terrible at technology. So perhaps the perk tree could give more nature/gardening/animal friendship type perks (and an option to reduce the anti-tech weakness) and chooseable weaknesses could include technophobe, all technology literally shorts out (literally, they visit a human friend and all electronics within X build mode squares breaks), afraid of cities.
Also, I'd love to see PlantSims have more abilities. Right now there's not really an incentive to become one, and to be honest I kind of lose interest around day 3 or 4. Maybe they don't need a full-on skill tree, but at least something that incentivizes me to become one?
[Edited to add]
I would also love to see ASPIRATIONS for new occults. For mermaids, I don't know, a nature aspiration that's Guardian of the Sea and a deviance or romance aspiration that's Siren? For aliens, a Knowledge aspiration of Xenoanthropologist or something like that. For Werewolves, a knowledge aspiration that's Master Werewolf--Regaining Your Mind, staying consciously human during the full moon--and a deviance aspiration that's about Embracing the Beast. For fairies, a nature aspiration about Guardian of Wild Places and a knowledge aspiration that's Keeper of the Lore. Etc.