For me, I'd love a game pack devoted to fleshing out romance. I'd love to have things like slow dancing back. I'd also love a more complex romance system like the way parenthood was fleshed out in Parenthood. As funny as it is that I can have one Sim marry another in a few interactions if they're both feeling flirty, I'd love if things like engagements felt a bit more earned.
My second most wanted would be more occults. Fairies, Werewolves, and Witches, oh my.
What about you guys?