As I told you, there is my headcanon of Zer0 \°D°/
I see him as an hybride human-alien with Eridium cavities which allow him some particularity, including a connection with his suit, class mod and helmet.
I imagined, since he is the result of an incompatible mix, he was born with some small handicaps such as a lack of vocal cords. By being connected to his helmet he can shape his thoughts into sounds and therefore speak :) (this can explain the weird sounds of his voice and the fact that he can change his voice like in the video of wimoweh). It also allows him to have a more complex view when he is invisible (the fact of seeing the enemies in blue and the ability to locate their weak point) hence, he never remove his helmet. And with his alien skin more sensitive than human skin on planete like Pandora, he try to don’t remove his suit too <3
Oh ! And I think he is non-binary °u° I though that his alien race didn’t had “male” or “female” and they reproduce a entirely different way (You will ask “how Zer0 was created ?” …Do you know test tube ? °u°). So Zer0 has a really different genitalia <3
I think I told almost everything °^° If not… then… sorry °u° or ask me.