I'm afraid I'd agree with Iso-G here (though I'm not the one to decide this).
This is an official forum hosted by the company... and it might be a problem for the administrators or global moderators to manage the posts they don't understand (and I don't mean answering them, but correcting incorrect information, removing offensive or unrelated posts, etc.)
Now, I certainly appreciate your offer, and I don't think you couldn't handle moderating the forum - but all the forums here should be manageable from inside the company (and I'm afraid we don't have the resources for a Japanese forum right now... but it might change in the future, of course).