Four more guys! That'll really help scale to a more gender-balanced group of companies! No insult to Sam, Garry, Emmet, and Justin who I'm sure are very talented. But given how Jessica Livingston talks about how hard it's been for Y Combinator to attract female founders and then they do something like this, I really have to wonder how much they're trying to change.
Because they have a hard time getting female founders, they have almost no female alumni to pull on. They want only the cream of the crop for this highly important role, and I can't think of a single female YC alum whom they think of as highly as they think of Sam et. al. Maybe Jessica Mah in a few years, but inDinero is too young for her to lose focus now, and she doesn't have as much experience as they're looking for yet. And I don't think they're comfortable inviting in people with whom they haven't worked.
This problem is a lot bigger than YC. It's not that women don't do YC, it's that women don't do startups. YC has a few hundred active startups to herd, and I think they just don't have time to address these problems of the larger startup landscape.