Was trying to think of a few ways to increase difficulty, but keep it scalar. Game starts off ok, but as soon as you get your first really productive unique girl, profit becomes automatic. Trying to think of a few new ways of increasing the difficulty, without making the early game too hard, so want most of them to scale with the size of the brothel/quality of the girls.
What a few of them will be based on is an idea of reputation/fame. Where you have a certain level of fame, and that opens new options as the game goes on.
1. Make high profit girls a bit harder to find.
Slaves
-Either scale the costs of the girls more, where the ones that make alot more costs far more (could be dramatic) or have several differnt tiers of markets. The first market are your fairly cheap girls (20-40g per customer) and whatever uniques might fall into that category. Once your fame is high enough, you get invitations to more and more select markets, with better (and more expensive girls). Probably have an cost to join those markets as well, either large first time payment or a set amount of gold for every visit.
Free girls, both walks and kidnapping.
-For girls you meet during a walk or your gang tries to convince. The girls stats are averaged, and that number is compared to your fame score. If it is too low, she thinks that she's above you, and won't work directly for you. Potentially you could give options at the time. Like she won't join you intially, but if you give her a large sum, she'll work for you. Or that she has a fixed house percentage when she starts to work, agreed on by contract.
-For girls that your gang is trying to kidnap, I might weight the combat skills higher, where the number that your fame compares to is something like (combat x 2 + magic x 2 + average score)/5. If she's a good fighter, she'll be harder to capture, and more likely to kill the gang trying. You could make it so that if your gang fails to kidnap, you have the ability to hunt her. Use the recapture job, and every week that you hunt her, her number goes down steadily. So in time you can capture her, but it might take a few weeks and gangs to do it. Also, initial obedience/hate should recieve a high temp modifier for every kidnapped girl.
Catacomb girls
-Similiar to kidnapping. But if you are sending your own girl down there, there's a chance that the monster girl will kidnap yours. Or if her rebellion is too high, be convinced to stay in the catacombs.
Level-based script events.
Right now it doesn't feel like the level stat does a huge amount, but with the LUA scripting coming online, this could be a great time for the girl to present a 'challenge' to you. Ideas for scripts.
-Demand better living conditions or a higher cut of the take.
-A slave girl could demand her freedom for the work she's done for you. You could accept or decline, but there would be negatives for declining. Also, if she's managed to save enough gold, she can try to buy her freedom. You can still decline (or even take the gold and not free her) but there would be legal rammifications for doing so.
-A slave's family could try to rescue her. A fight ensues, with the potential to capture family members. If the girl wasn't legally enslaved, they could also go the authorities.
-A customer could fall in love with a slave and try to buy her from you. Again accept/decline, but if you decline, he could attack or try other ways to get her from you.
-A noble falls in love with a slave and tries to buy, or blackmail her from you. Declining could get you in trouble with the authorities, or have the noble put his house at war with yours. And if the noble is a lady... well, you might have a chance to add to your brothel (but face alot more heat in the future)
-A girl gets injured badly. Would require medical care. How much you pay defines how long it'll take for her to heal.
-A free girl wants to retire. You could either let her, agree to higher pay, or enslave her.
-A free girl falls in love and wants to stop whoring and start a family with the customer. Again accept/pay/enslave, or you could kill/enslave the customer.
-A noble falls in love with a free girl, and she loves the noble as well. If you allow them to marry, you'd have a powerful ally.
-A noble falls in love with a free girl, but she doesn't love the noble. Do you protect the girl, facing the nobles wrath, or create an alliance.
Increasing the interactions with the authorities in Crossgate. Right now it's just bribe and forget, or just pay the fines and forget. They could do more things, such as increase your taxation rate, free all the girls in the dungeon, free individual girls, etc. Would take a bit of work, but you could also try to fight off the authorities with your own gangs. Expect to see alot of raids/attacks, but you wouldn't have to pay taxes anymore, and be free to do whatever you want. Pay enough money in the future and you can make peace with them. Maybe even have an end-game where you fight the police, and win =).
The matron could try to stand up to you for the girls sake. Increasing rebellion or better living conditions. Or make a less on the matron in the dungeon.
Attacks from the monsters in the catacombs. Fights, thefts, kidnapping in both ways.
Just a few ideas, chip in any you might have.