Is Emma Thompson a founding member of the Men In Black?

Emma Thompson is reportedly joining the cast of Men In Black 3. And it sounds as though Thompson's character could turn out to be a huge part of the MIB mythos. Spoilers and speculation below.

According to Deadline, Thompson has been cast as Oh, the leader of the MIB. And we're wondering if she's actually the original leader, since the third MIB movie is supposedly all about time travel, back to 1969. Will Smith is sent back in time — for reasons unknown, but we're guessing they're zany — and is forced to interact with a more youthful version of today's MIB. In fact Josh Brolin has been cast as a younger version of Tommy Lee Jones from 1969.

So maybe Thompson is the 1969-era boss. Which leaves one question: who do you get to play her underling, the much younger version of Rip Torn's character Zed?