I've played way too many games with character creators that let you change everything but gender later in the game, and honestly, I can understand why.
It could be lore breaking. It might result in inconsistent dialogue. The gender you choose for the protagonist might determine the genders of other characters. Character creation choices aren't one to one between the gender options, meaning you have to entirely re-customize your character. Etc.
I don't care. I want the option anyway.
Also, ideally, with presets created so I can go back and forth between forms without having redo their appearance each time.