If sexual attraction can be used (and it for sure plays a role in interactions sometimes), than not only the sexual orientation has to be modeled but also sexual visual preferences. There are a lot of men and women in exist who would receive nothing if they "flashed their boobs" in front of me. That cannot be simulated by the roll of a dice because it's an all or nothing thing.
So the effort would be high to implement such a system and the gain would be quite small in my opinion, if you wanted to avoid extreme stereotypes.
At this point, we've theorycrafted a complicated enough system with so many variables that it really just returns to: Make a Persuasion Roll. The variance in the d20 roll will account for their orientation/preferences.
