I feel like we haven't seen him because it'd be too easy for Jeph to accidentally slip into gay stereotypes with that character. Also, whenever I've imagined him I picture him looking nothing like Marten. Probably because he looks like he gets all his looks from his mother.
Actually, I just realized I imagined someone who looked surprisingly like his former boss. And then I realized, all of Marten's bosses in the comic have been homosexual. This is an interesting phenomenon. Perhaps he tries to think of his bosses as somewhat of a parental figure? So his next boss will be a dominatrix. Or maybe Tai secretly is.