Actually, unless I somehow hallucinated the whole thing (and seeing as how I don't do drugs or alchohol, that's highly unlikely) there already is a way to do so for male highlanders. I saw two of them with eyebrows in mor dhona, and the sight of it was so different it caught my eye.

They looked... terrifying.

I think I'll stick to my hairless brows now, thanks.

(most likely it's not an option unless you use the hairstylist, who has an expanded range of choices than the character creation.)