I really don't think we'll ever get genies and that's kind of a shame.
they've given up on their one life state for every expansion pack and only add them when it makes sense, or when they think it makes sense. I still think fleshed out plant Sims would have been perfect with eco living.
If they do ever come back, I'd honestly be fine with them being just like Sims 3.
I really don't care if playable ones can make wishes, but for npcs they should have
Wish for romance: fall in love with the person of your choosing. Failure gives you a stalker that shows up on your lot at night, leaves love notes, snoops through your trash etc.
Wish for fame: gain x amount of fame point on success, failure decreases your reputation and earns an enemy.
Wish for fortune: 100k simoleons just like sims 3. Failure causes your next bill to be substantially higher, failure to pay back or course causes the repoman.
Wish for children: You become pregnant on success, whether male or female, it's magic so rules don't apply. If you are married the baby will have both sims genetics, which would be useful for gay sims. I'd love for failure to turn you into a teenager again, that's the only thing I can think of.
Wish for youth: You become a young adult again on success, this wish is only available for adults and elders. On failure you age up, if you are an elder it instantly turns you into a playable old age ghost.
Wish for popularity: Three random friends will be made for your sim on success, three enemies on failure.
Bring back the dead: A sim of your choice is ressurected, but on failure they become a zombie, another new lifestate that can only be cured with ambrosia, or a witch's dedeathify. (Witches also get a new spell, reanimate which brings back sims as zombies)
Wish for peace of mind: Your sim.will.forever be fine, no longer constrained to the emotion system, similar to the vampire power. On failure though, your sim will have a tense moodlet that lasts 7 days. (Can be shortened with appropriate activities.)
Wish for more wishes: Your wish is granted, you get 1 additional wish, cancelling itself out. However sometimes you get 2 wishes from it, but it can only be done once a day.
Set the genie free: Requires high friendship. If it fails, YOU become a genie.
