When the girls-not-buying-items thing is fixed, this will allow us to give money to slave girls, who can then use it to go equip themselves in their time off. Ideally, the purchasing script would have them buy the best improvements that they can given the cash they have to fill out their item slots. Girls who get rich should have the best dress, best shoes, best jewelry, etc that money can buy. Since slaves typically wouldn't earn any money on their own, they would have to either be manually equipped by the player or be given cash with which to purchase equipment. Since the number of girls is exceedingly large, I'm guessing that most players won't want to equip each girl manually. Giving them money to spend with a good purchasing algorithm makes sense.
Now if we can make items relevant for maxed out girls, then the whole thing would really be worth implementing.