Perhaps adding in other types of NPCs into the mix would be a nice additional challenge as well such as police that once noticed is an instant game over, as others have said other female NPCs.
Also I feel like their line of sight is too short or lacking because at times I can see them from the middle of the road yet they can't see me? (Or is everyone just partially sighted? XD)
Maybe add in a daytime mode where everywhere is alot busier to add that extra challenge?
I would also suggest adding in some kind of mission or objectives would be good, I know there are the existing challenges but I feel like something else would be good to have in there as well like for example 'reach the crossroad and masturbate whilst naked'
Finally I would like to be able to customise the character (even if its just a selection of pre-set shapes and sizes)
Those are my thoughts on this so far