So the opposite of tiredness would be...energy?
I had been thinking "endurance", but "energy" might work better

I'd like to suggest that you give bonuses and penalties for happiness and energy to work done. For most tasks give a 5% bonus for having over 90 in either stat. Give a -10% penalty for under 50% in either stat. The penalty rises to -25% as you approach 30 or less in each with a refuse to work at zero.
You're way ahead of me. The plan is to make customer supply strongly depend on the brothel's reputation, and to make the rep depend on keeping the customers happy. At the lower levels at least, a girl who is pretty, healthy, happy and energetic is going to get very few complaints regardless of her actual skill. So looking after your girls is going to be key to building the reputation you need to get established. On the other hand, a girl who is sick, unhappy and exhausted is going to have a hard time pleasing the marks even if she has decent skills.
So the player will have an incentive to treat his girls well

It might be nice to put in a few special activities in town. Say if you get in good with the government faction you can pay for one of your girls to visit their exclusive club for a day of pampering (big energy bonus, mild happiness bonus, and a slight bump to a random stat like reputation, charisma or beauty).
I have some thoughts along those lines. There's a banker who before he'll advance any serious money, he'll want to sample the merchandise first. And if it's not up to standard, you'll need to come back when it is. And there's going to be a few discoverable locations, some with events attached, some just merchants. Then there are going to special commissions - parties that need party girls of various qualities ... or that's the plan, anyway. I have a rough outline of the events system working, so the big problem remaining is tying the triggers in to the timeline. That and writing all the events of course

Maybe the scientist have a private amusement park (big happiness bonus, small energy bonus, slight loyalty or love boost). Each factions private play area should be unique. Visits to each would be accessible after you've done work for each faction. Each visit would take a girl off work for an entire day and have a cost so the benefits should be worth it (like the major benefit be a long term boost that wears off after a few days).
There's going to be a lot of scientists. They may have one formal lab, but in practice it's more like a museum than a laboratory. The real action happens in dozens of little labs and artificer shops scattered across the Air Quarter. But there you'll find roboticists, plastic surgeons, resurrectionists, vivisectionists, mind controllers and plain old perverts. All of them with some sort of deal they can make with the player
