I like those ideas about dropping combat skills and constitution near the end. Perhaps raise the chance of small scars? (Stretch marks?) As for looks, I'm either way, I'd like to see a slight drop in the looks department (pregnancy isn't as wider fetish appeal as, say nice figure), perhaps giving the girl the temp. trait of preg/insem to add a fetish and put in place these changes? (Although I think that'd be a given seeing its the easiest way) If you wanted, you could make two/four traits for early/late preg and a different set for insem, needless complication? If we're just adding in different traits, I don't think so. Gives the preg/insem some depth. However, can you add time-sensitive traits that develop? I haven't seen that so far.
On another topic, disease. I've had 1 girl in the hours and hours I've played this get a disease, and she was low health (single-digits) Is that a perquisite? She died before I could see any effects or trait blurb, but I thing diseases should have a much higher occurrence. I never have to use the Cure for XYZ, cluttering up the store items with useless items effectually. Brothel girls may be more immune, checks and such, but stripper/street girls should have a high(er) incidence of picking up diseases.
This may be planned, but also, if we are getting a drub lab building (?) we could use the girls in a good way to provide health care, even have a doctor (perhaps a new trait to train up the girls working the in lab?) to perform safe abortions? If we wanted to make use of a potential 'doctor' we could make them male only? Use up some of those male children. We could also make the more serious diseases need one, such as aids. Using girls in the lab for health care, a potential job would be providing care to raped/goon attacked/fresh out of the dungeon/XYZ girls, like nurses. Hell, forget using the drug lab and make a clinic building. Just throwing suggestions out there, I think much more fragile girls (not the trait, but maybe you could use girls, *nurses?* to rehabilitate girls that pick up that trait?) Would mean a vast difference between evil (uses up girls like kleenex) and good play styles, while adding a considerable expense to the running of you empire (Which would be optional, according to you budget/play style). A clinic could also be used for your gang-members, but I you want to limit them to potions, I guess that keeps the two sides separate. The gangs don't have *individuals* worth anything, except if you add in girls/sons to them, but thats another story for later.
Sorry if this is in the works/too much to code, and the doctors being male thing is just to use the rather annoying sons, it's always disappointing to get a boy, what a loss of income. They can be girls too, using up nerdy girls with high intelligence, or making it child-only could be good, are we getting a nursery/dorm/added depth with the children? Perhaps you could have a list of *school/training* options for a young child, from that building, and pay weekly for them to develop into specialists such as Doctor/Drug Cook/Matron/Teacher (are matrons still in the works or are *Madames* superseding them?. Teacher? Well why pay for children's tuition when you can just use a spare person and save on costs?!) Other skills like martial arts/massage/beauty school/dance/XYZ wouldn't make a specialist, but give you highly skilled children that you can put into use in your operations (Gang Leader/prostitutes/strippers/what have you) A Teacher could come from extra training from a field, say first a girl learns dance, and then you train here to Teach. She can then teach dance at living cost rates.
Making a specialist be capturable from the territory event (man sells daughter ect) or making a customer who's a specialist who gets caught not paying could result in the option to *force* employ them, to get cheap workers in a more evil and far cheaper (faster?) way.
I know that may seem a lot to do but this would improve the difficulty, while giving the option to micro manage or just not care. You could use your play style to influence how you implement these things, without having to go into too much detail. And this thread is 'suggestions for difficulty', so thats my *rather long* two cents. (Got a bit carried away here)