My objection isn’t to how you can or can’t code it. My objection is that I don’t see it as beneficial to the game to code it.
As regards romance options, these are my thoughts, and I say this as someone who plays both gay and straight characters, male and female (usually female, preference varies):
Referencing Choice of Broadsides - I don’t want Beatrice and Brendan (one could pick the other two, but that’s the one I went through when I first played) to be merely the “Historical gender roles/opposite of historical gender roles.” options - it ruins for me what little there is of them as individuals for them to be written so that they are literally exactly the same except for name and pronoun.
I think the fact that "boyish charm’ does not conjure up the same image as “girlish charm” - whether one likes either, both, or neither - is part of it.
I don’t think that people having to date a gender that they’re not attracted to in order to date Donald ( http://magicaldiary.wikia.com/wiki/Donald_Danson ) is in any shape or form a bad thing, unless failing to date Donald means something in regards to the completion of the game. The player who is only willing to play the game as (using my RL gender and orientation) a straight male and never deviate from that so as to experience dating one of the male characters is limiting themselves, and self-imposed limits are the problem of the one imposing those limits on themselves.
So given the option to vote, I vote against anything that makes dateable NPCs change genders based on anything the player does. Especially if playing a gay or bi character in an accepting place, so you’re not exposing yourself to anything by playing a m into Dave vs. a f into Dave. I’d be heartily in favor of (in a modern day-ish game) playing up the tolerance aspect for that reason, if there wasn’t any particular reason to explore dealing with intolerance here. Save “bigotry is normal” for less cheery settings - high school being high school is enough.
Different people are different. But that’s my vote - it makes it less enjoyable, not more, for “Alison” being just as easily “Andrew” and hair color having more relevance to whether or not I (try to) date someone than their gender and sexuality.
.