Personally, I would also like to see a bit more complexity, like the ability for a girl to perform more than one sex act per client, with adequate bonuses, for example if she does blow job and normal, she gets the price for the two + a bonus of 1.. blow job and anal a bonus of two gold, etc. Maybe this could be based on one of her stats, like intelligence:
0-10: maximum one sex act per client
11-20: maximum two sex acts per client
21-30: maximum three sex acts per client
31-60: maximum four sex acts per client; minimum two
61-120: maximum five; minimum two; high possibility of at least three
121-240: maximum six; minimum three; high possibility of at least four
241-299: maximum six; minimum four; high possibility of at least five
300: six all the time
made based on the six available from your list, could scale differently, but 300 should be something like the holy grail, or maybe 300 could be max girl skills, then the cap get's raised depending on traits and items, and you can only get all the six sex acts per client if she has max with items and traits included... maybe a 360.. or more idk...
Also another similar game had the possibility to have children with slaves, that would be neat, then you could have them start working for you from 12-16-18-21, maybe cleaning lady from 12-16, stripper 16-18, 18-21 personal daddy training, with a special event at 18 when you get to chose if you auction her virginity, so you get to display her from 16-18 to attract the interested clientele, then auction her virginity or simply her as a slave. And at 21 she can start to work legally for you as a prostitute... with the 18 auction being more of an underground thing.
She could start working sooner, if your morals are comfortable with that

maybe black market high risk stuff. Btw I am proposing this mecanic with the current slow paced one day per next, I think it would provide some nice end game-ish rewards, maybe you could also set a maximum age to play, unless you father a boy child which would have a 0,01% chance, 1% if you get some high cost items..