A few more, stat related this time:
Skills, Traits and Experience: Branch experience and levels into different areas of expertise, similar to before, but a little different. Instead of "service" have there be things like "masseuse" "bartender" "security" "waitress" etc. When experience gets full, they raise a level in that skill area only. Learn by doing.
Ah but here is where it gets interesting: Traits would affect the rate of skill gain. A high "combat" skill would gain skill in "catacombs" faster. "Combat" and "charisma" makes for faster learning in "security". "Beauty" and "Agility" would effect skill gain in "Stripping" and so forth.
So having high traits would not give a girl an instant-profit effect. Rather, it would make the girl advance in some skills faster. Having a low trait would not lock a girl out of a job, either, it would simply make her take much longer to get good at it.
Libido: Actually leaving that in but altering it's functionality to keep it interesting. "Libido" would be a fluctuating stat. It would continually increase until the girl actually has sex. Having sex would satisfy her & thus lower her libido in proportion to how good the sex was for her. Other traits could modify this, too; for example, "nymphomaniac" would increase libido at x5 speed, while a trait like "frigid" would make it lower at only 1/3rd normal speed. So how does affect the game? A girl with a higher libido would earn more tips whilst whoring, naturally, due to enthusiasm. A girl with a lower libido would make less. Higher libido would be more likely to willingly put out for the player avatar, low libido would "have a headache." And (this is where things get a bit too realistic) a girl with a high libido for too long may just start boning the customers even if not assigned as a whore. Which could be a problem when your star waitress, for whom being only a waitress you felt no compulsion to buy anti-preg potions for, starts screwing the customers behind your backs and gets herself knocked up. Or diseased. Or both. Conversely, girls with high libido gain (see "nymphomaniac" above) would naturally make better whores because they'd make more tips per day (since their libido is refreshing faster, they'd enjoy more sex with customers before becoming pooped-out boring lays by the end of their shift).
Magic: Magic should be an interesting stat, an asset in some girls and a liability in others, depending on how it is treated. Magic could be used to enhance the effects of items that the girls (not the player) feel have a positive effect (beauty rings, combat enhancers, healing potions, etc) while lowering the effects of items that girls (not the player) feel have a negative effect (slave bracelets, control collars, mind control effects, etc). So one one hand a high magic girl would be a bonus so long as she is willing to work for the player, but when she decides to get rebellious she becomes a lot harder to control as well.
Bribery: Who says it has to be gold? Make an option for "government discount" Your brothel now services the mayor & the cops for free. Bribe effectiveness is based on how satisfied they are with your girls. (TMI: This is one way that real professional pimps/madams do it.)
Beasts: Okay I've captured some beasts but what if I, personally, find beastality to be icky & don't want to have it my brothel? What do I do with these critters? Well, I could sell them to a zoo ($, positive public image) or I could have animal pit fights for gamblers ($$$, negative public image).
Inventory Management: Highlight girl's traits that are being given/altered by currently equipped items. Easier to remember which traits are natural and which one's a item-based.
Legitimate Front: Money laundering effectiveness should be based as a percentage of legitimate income the place is bringing in. Meaning that the Bar (and anything else innocent business you feel like adding) should have it's income create the first variable that effects how much of the income of the Brothel (and other not-so-innocent businesses) can be laundered. A very profitable Bar (and Gambling Den, if gambling is considered legal in your game) could launder more money from the shady end of your income flow. Likewise, if your Brothel is bringing in twice as much money as your Bar/Gambling Den, then expect to be able to launder a lot less - and gain more Suspicion from the government as well. (TMI: Again, this is how reality tends to work.)
Jealousy: Having six different girls thinking that you're "their true love" should (at least potentially) cause problems - just ask any musician. Higher love should require higher upkeep/pay/gift bribes/etc to maintain as the number of girls that like you increases, otherwise is begins to decay back to indifference.
Philanthropy: Okay so you've got the mayor in your pocket, but what about the general public? Well, there is obviously advertising, but what about your image? Donate some money to the temple, or the orphanage, or a homeless shelter, etc. Your good/evil ratio in the public eye will improve, and possibly even make it easier to recruit new girls because of it. Again, in real life, look at how many soup kitchens Al Capone sponsored "out of his own pocket." Why did he do this? Because a bum who relies on you for his next meal is not going to tell the cops squat when he sees you sticking a large bag into your trunk.
Monster Girls vs Human: Give your brothel an "Exotic" rating based on the ratio of how many of these two types of girls you employ. Then assign a similar rating (random) to customers who come in. Some people may find your circus to be great, while others may be freaked out. Over time, that random variable in customer tastes will change to whatever your brothel's rating is (basic economics of supply & demand), but the change would indeed take some time. Completely changing your staff overnight may have negative consequences.
Legality: Akin to a "difficulty" setting, but more tailored to the game. When starting a new game, decide what kind of city you're in. Is it a wild freeport where prostitution, gambling, beast fights and slavery are all perfectly kosher? Or is an uptight temple-dominated area where everything is considered a crime, there is no slave market, and the government is always up in your grill? Or is it somewhere in the middle, for instance, gambling is legal (so your Gambling Den would never get raided by the cops) but the Brothel itself is still verbotten (and thus at risk)?
This would, naturally, effect everything from bribery to public opinion to how many customers you get per day. Before writing either side off, though, consider that the "anything goes" town is going to require you to have a lot more girls doing security & gangs stuck on guard duty as well, while in a strict town one you've spent enough to put the mayor in your pocket then you're now on easy street & pretty much immune to acts of violence from the opposition.