Dragomer asked: What if the girls decided to go full time as Zuko's sex pets? What if Zuko was the one who wanted them to?
The only difference I see between these scenarios is that Zuko would give extra praise to the girls if they had that idea on their own.
Head-pats, belly and back rubs, calling them "good girls", and feeding them little things like grapes (and getting his fingers sucked and/or receiving a loving, playfull bite once they're satisfied) would be a every day thing. Also, they're all getting collars they wear 24/7, and Zuko will only not do their hairs himself when he's really busy and/or in a hurry. Despite them being "pets" and not Fire Ladies, Zuko will occasionally ask their help with political stuff, and praise them for being "clever pets". Obviously, the sex is very rough and people are shocked whenever they see the scars on all four of them.
Anyone who gets too close will get be growled/hissed at (god help you if Zuko tells them to attack you. He trained his girls very well). Mai will be loving to Zuko and the other girls, but just be polite to the people around them. She'd warm up to the ones that are good to Zuko and especially to Ty Lee (I NEED protective Mai). Obviously, Ty Lee is the super friendly pet that looks harmless but can wreck the shit out of anyone.
Azula is definitively the most "cat-like" of the three. No touching her when she doesn't want to be touched… but Zuko can't ever ignore her or she'll dig in her claws on his leg until he pays attention to her. And it doesn't matter that she said she didn't want affection at the time - that doesn't mean he can go be with his other pets! She'll 100% throw herself between them to get all the cuddles. She gets punished when she acts out, but she just doesn't learn (and thank God for it, because the other three love their little brat). She ignores everyone outside her little group, and people outside the foursome don't really understand her way of showing affection.