I would imagine that it would require assigning some kind of masculine-feminine value to every character creation trait
Masculine body > presuming male
Feminime body > presuming female
Beard - overwrites body > presuming male (maybe except Dwarves)
What other traits would you concider?
I think we’d also have to consider hairstyles (for all that many hairstyles can be worn by all genders in FR there do seem to some that are more gender-specific), clothing (some clothing - eg barbarian starting gear - will reveal the body shape, whereas other - eg scale male - might disguise it) and face (some faces look to me more masculine and feminine and others more ambiguous).
And if the game is going to introduce the concept of misgendering or passing at all, then I think it’d have to let us create passing trans characters as well as ones that would be more likely be misgendered. The fact that that’s actually tricky to do, partly because of the way clothing is reskinned depending on the body type of the person who dons it, would be one thing that would need to be addressed. But if I think about how I’d try to create a passing elven trans man, for example, in the game now, I’d choose one of the more androgynous elven “female” faces (face 5 for example), select a hairstyle that wasn’t too obviously girly (probably a short one, though I think that’s more to to with my own gender coding than Faerun’s), and put him in one of the armours that hid curves as best as possible given the options we have (scale mail, say). Having done my best given the tools available to create a passing trans man, I’d be annoyed if he was consistently misgendered just because the base body type I’d picked for him happened to have boobs. But if the game somehow was sophisticated enough to recognise this character as passing and have NPCs see him as male or at least non-binary, we then have to consider that someone could create a character who looks exactly the same but as a cis woman. Would or should the game then have her being misgendered?
Plus there’s the complexity of how different NPCs might read gender differently when it’s more ambiguous. It would seem unrealistic to me if they all took the same view, particularly when they were of races that were physically quite different from the PC’s so would probably be less alive to gender cues. In fact, if we are really going to try to be realistic, I’m sure there are some characters and races that would get the genders of our non-trans characters wrong (or wouldn’t bother trying to get the gender right or think about it at all) even if our characters would be very obviously a specific gender to anyone of their own race and culture.
Question is, if Larian would be capable to tune it well enough to not "cross the line" ... then again, looking at oathbreaking conditions, maybe it will be better to leave this Padora's box closed. :-/
That’s my feeling, yes. In fact, the only way I can see this working is not to have the game try to work out what gender our character looks like, but to let the player decide with yet another option what gender NPCs would consider the PC to be. Or perhaps just use the exact option it seems we will have, which is the “identity” selector.
True, the options we have now don’t let us create a non-passing trans character (or at least don’t show us the effects such a character would in actuality likely have on the way NPCs spoke and acted), and perhaps this is something that could be added. This would require the addition, as we’ve alluded to, of a fair amount of content to represent the gender coding of all NPCs for whom it was relevant (as mentioned, I don’t think it would be reasonable to have this as a blanket option for all), and dialogue options in a variety of places to allow the PC to correct NPCs who misgender them, plus those NPC’s responses. It feels like it would take a lot of thought and work to do really well. And the question we keep coming back to is, does anyone really want such functionality? It doesn’t sound to me necessarily bad (and actually, depending on how it were implemented, I might actually want the opportunity to have it affect my cis characters too) but it’s not something that would make it high up my personal priority list. Unlike the option to create a trans or non-binary character at all, which I agree with Gray Ghost should be the default in this day and age in a game that purports to give players flexibility in character creation.