So guys...on the Kate route, I reckon that three two side routes remain uncompleted: Villa, Sophie, and Maria and Peter (edited, I managed to get that one finished in the meantime...)? I have all the other opportunities marked "finished" except these three two.
edit: Ok seems I got luckier in my search on this thread, for anyone who wonders, the Sophie and Villa quests don't show as "finished" even as you end up stuck in the following loophole scenes, which seem to be the final ones for now:
-Sophie eating Kate in the school corridor
-Kate remaining alone as she cleans the villa, with the occasional sex in Alice's room and BJ in Max's and Lisa room with the option to continue or share Big Max with Lisa.