Just gotta say that I love this game, though there are some things that bug me about it. First is the age thing. While I understand the desire to keep the minimum age at 17, it is rather irriatating when the status screen shows the wrong age, espically when you know the age of the girl.
What I suggest then, would be to allow the true age to be shown, but do not use any loli girls in the actual game.
This would allow you to maintain the your stand without breaking the illusion of the game world. Those who wish to can either create their own girls, or download the girlpacks.
The other thing I find wierd is that currently, the only difference between the girls is that some are bought from the slave market, some found (or kiddnapped) from the streets, while the rest are from the catacombs. Other then that, it's all the same. What I suggest is that there should be some kind of different levels to the girls. Goddesses and demons should not be on the same level as other mere mortals after all.
I suggest the following division,
Level 6 - Goddesses and demons (Ah! My Goddess)
Level 5 - Supernatural beings (Touho)
Level 4 - Other races (Elves, monster girls)
Level 3 - Cybot/robots (Chii, Andriod 18)
Level 2 - Combat type (Naruto, bleach)
Level 1 - Normal (Other type of girls)
Special Level - Royalty (Queens and Princess)
Furthermore, Your ablity to house those girls would also change throughout the game. You start off only able to capture and whore out normal girls. As you expand and learn, you'll then take on the challage of breaking in combat type girls, and so on. Different level of girls would require different type of eqiuments and rooms.
Normal girls may only need a cell and a whip, for instance, but combat class may need a full dungeon. Supernatual girls and monster girls will also need special gear catered to them as well, amulets and magical restrains and so on. You might only be able to access Royalty slaves only in certain situations, like say a VIP section of the slave pens that is only accessable when you reach a certain measure of importance or influence in the city.
Factions is something else I'll like to see in this game. Something like having a set bonus when you have, say, two girls from Naruto working in the same house, or on the same job. Maybe special combos can be unlocked and used, like say, Euphemia and Cornelia from Code Geass. As they are sisters, there'll be a special event or something when you aquire both of them. Stuff like that.
I'll also like to see options for the enslavement of unique chars fleshed out. Say Chun Li is going around challaging people into fights and winning all of them. How would you go about enslaving such a woman? Cheat during the fight? Slip drugs into her food and drinks to weaken her? Or train yourself to such a level that you can beat her fair and square? Such would also determine how she'll view you as her master.
Events affecting the world at large would be interesting too. From small events like a certain all girls inn going out of busness, evacuating the tentants onto the streets, to the invasion of a country leading to an influx of slaves, things like that.
Of course I realize that many of my suggestions are not very pratical at the moment, but this is something I would like to see in this game. Just something to think about...