Actually, yeah, that's relatively easy.
It kind of breaks the immersion a bit because the text will still refer to them as being exclusive to the King.... but I'm guessing people don't care much about that.
I can post that a bit later when I'm at home.
LATER THAT DAY: Here it is. Throw this into your game directory and I think the King will then take girls who have had sex with other men.
Disclaimer: This is just something I threw together for fun one afternoon, and I have not meticulously tested every possible turn-out, so please keep that in mind. Also, this patch assumes you have the Leane 2 full English translation installed. I have no idea what it would do if you tried using it without the English patch.