You know, I've thought about that possibility, basically keeping Philip as the ultimate spy whose real origins are never really known? But I think ultimately it would wind up making him seem like less of a character.

For instance without the context of his real background, he just sounds like a guy who doesn't have her upbringing and could be Stan Beeman. Like Elizabeth has her opinions because of her very specific (harsh) background while Philip's aren't. Like he might as well just be reflecting back the culture he's in or something.