Definitely I would love to see mermaids get updated. I was having a conversation with someone the other day, who had stopped playing after the Sims 2 pretty much and never got to 4, about all the pros and cons. And supes came up. And how disappointed I was with how mermaids were done.
And how they and aliens were the only ones to get such a crappy add in. Both being brought in as an addition to an expansion pack and not being ever fleshed out the way the game pack introduced supes were. I mean yeah wolves have that weird fury that would've made more sense as a hunger base. And would've really worked as an opposite for the vampires' thrust and even the mermaids' lone hydration bar. Making all of them based on an intrinsic need of their species that affects behavior and powers. But I digress.
I would love to see an underwater mermaid kingdom that only has like idk two lots on islands above water. And you access them through portals like the one to the spellcaster realm or that bunker elevator type mechanism from the wolf pack. Non-mermaids would have to Sandy Cheeks it with a helmet or airbubble to live down there easily. Something cool that they can eat in. Non-puncturable.
Except maybe if you buy a cheap one and that's a new death. Or you open the helmet outside.
The houses could have air in them. Or rooms with air in them. Like in those underwater caves. We could have new versions of Meres. Ones with legs but fins for ears. O.G. Laguna Blue type or some Urusla types. A pet fish. Your dolphin friend could come over without you having to call them on the shell.
Mermaids could have shellphones instead of cellphones.
And if they decided to fix aliens from there, they could make the alien world an actual world. Or make a sister world that is playable. And the rabbit hole one just be the tourist trap that all the human sims go to and think they've seen everything there is to know about their world.
Meanwhile next door they're riding hoverboards, attending school on a space station, the salon is where they perfect their human disguises, and they address the whole abduction and return pregnant thing. Maybe there's just a club with new super flirty lot traits, and a what happens in Sixam stays in Sixam rule, and the humans leave forget and boom baby in 3 days.
Either way I'd love to see these both fleshed out. And werewolves fixed bc I literally can't bring myself to play, and it's not even just bc of all the bugs. I waited years to be disappointed.