It seems like MMF really is the negative influence. I tested it by having the idol become a sex friend and lover with the two guys in her area, had both of them become friends, and all three of them have max satisfaction and charm, but still couldn't get the 3P option. I suppose next step is to try and get all three of their dissatisfaction up, but that feels like more of a hassle than it's worth.
On the other hand, FFM can be achieved without hiring a gigolo, didn't really keep track of what the requirements are, but at the very least all three have to be friends with each other.
Oh man, a modern Biko with character customization would be very welcome. I still have the installer for Biko 3, but I don't think it'll work well on modern systems. I remember its performance was terrible on an Phenom II x6 1090T despite it working smoothly on much older hardware, was probably reliant on some instruction sets that went the way of the dodo.