More co-authoring?

During the long, the stimulating (perhaps ongoing) exchange over the relationship between (philosophy of) physics and metaphysics Jason Turner (one of the leading young metaphysicians) asked "what, in practical terms, would you recommend a would-be metaphysician do to get up to speed on physics?" This (genuine) question was echoed by a graduate student. Here are some reflections designed to stimulate further suggestions:

1. Some departments in HPS require a MA in an adjoining field in order to get a PhD. A lot of philosophers of X (PoX) fit this bill. It is worth asking if besides genuine competence in modal logic and set theory (perhaps probability theory), PhDs in metaphysics shouldn't obtain a MA in physics (or some other science). This would undoubtedly come at a cost (history, alas?), or it would lengthen the PhD program against the deplorable (!) world-wide trend of shortening PhDs. Even if the opportunity-costs were manageable, I am not sure if text-book knowledge of some science would really solve some of the deepest problems. 
2. Co-author with a scientist or PoXer. While co-authoring seems to be quite normal in metaphysics (and I think this is a great trend), co-authoring with non philosophers or PoXers seems still surprisingly rare within metaphysics (I think). It is far more common in philosophy of mind, philosophy of biology, X-phi, moral psychology, bio-ethics, and maybe a few other areas (some philosophers of economics also team up with economists). 
3. Cultivate reliable sources within an other discipline. During the last decade I have almost daily email with three economists (and a wider circle of economists, including historians and methodologists that I pester much less frequently); they ask me about philosophy, I ask them about economics. [At one point I corresponded with Milton Friedman.] Surprisingly enough, in the beginning the economists taught me a lot of philosophy; more recently I have started to teach them a bit of economics. Sometimes our research converges, other times not. They always treated me as if I knew more than I did (thank God for Wikipedia & Jstor!), and I always asked focused questions. It's an amazing, ongoing learning experience.

Other suggestions?