I also had the issue with the house improvement after I replayed with cheats. Could be that I skipped an upgrade, I couldn't buy them afterwards though so my lvl 5 girls didn't want to shoot anywhere.
My opinion on the game: The game is done quite well, I like the almost infinite customization possibilities. On the other side this made it so that the girl's look didn't matter at all (you could always send her to the surgeon). This made the girls a bit bland because in the end only the stats matter.
The tatoos on the other side were really cool because they were unique and you could "catch them all".
Now, the main problem I have with this game is the missing climax: Really, as soon as you've fucked one girl you've had all of them: I didn't see any change in positions and a lvl 1 girls fucks just the same (and might even look prettier) than a lvl 5 girl. That's a bit of a pity because as soon as the player realizes that at like lvl 3 he's like "sooo... why should I keep playing?".
Giving the player all these options might hinder the fun of playing the game actually.
I'd suggest some kind of arc of suspense: Hookers from the streets might be really heavy on STD, so the main character can only fuck them with condom. They'll also be rather unengaged, just lying there while the player ploughs them.
Maybe some items and the surgeon are also only restricted to higher tier actresses.
That said leveling up the actresses right now is way too expensive and time-consuming, you can find new ones that are way better than your starters very quickly once you have the stats even if you don't cheat.
I liked the "unique characters". Sadly I somehow can't get the one I actually want (the blue-haired one from the beach). She just thanks me and keeps me open as "option C", but nothing more. A quick replay with cheats yielded no other result. Help?