Another quick suggestion:
Optional genital pubic hair.
The player character is an adult and the default character model is shaved for lack of a better description so it makes sense as an option and also may reduce the chance of someone mistaking the main character for a child / teen without context.
In practical terms it could be a purely visual change:
Hair color is uniform - if one is black then both are black.
Visible when not wearing panties depending on camera angle.
Does not hide genitals depending on camera angle.
See the linked image for a suggested shape:
Link is more or less safe for work without context.
Edit: rewritten to fix my inept writing ability.