Your comments

 If Fek could include a system where we can optionally write these in if we want to or just continue on without bothering with any of this, that would be great for all of us, right? So if anyone wants to play it the RPG way the option is there.

 And if it affects any part of the actual game at all aside from helping some of the folks feel immersed (I'm pretty sure I can quote an example from TiTS's current character customization system but I'm not sure) don't think this will change anything except the pronouns, so hopefully that's not too much trouble.

 Off topic but on conversation, I'm under the impression that 'Trans' and 'Cis' aren't gender identities in and of themselves, though. Agender, 'nonbinary(big big blanket)' and 'androgyne(gender-neutral is better recieved as a gender identity's name, as far as I know)' are, but...? Maybe 'Transmasculine/transfeminine' ect was the word you were looking for, OP? Please do correct me if I'm wrong!