So in the absence of any 100% confirmation I am still happy to accept this has the "ring of truth" about it. The model is being implemented elsewhere in the world with the SA and DE branches becoming the super branch for their continental regions.
Printing the mags in Japan maybe cheaper as I expect the number of mags needed in OZ/NZ has dropped considerably due to the use of online materials and the reduction in issue numbers. Don't forget as well that the Japan branch would be looking after the rest of the region so you get economies of scale.
Real estate in Australia, especially Sydney, has rocketed in value over the past 10 years and the opportunity to cash in on this has never been better. A smaller branch with less overheads again fits with the recent changes elsewhere. No where has anyone said the branch is actually closing.
I accept that the risk presented by the ARC is probably not the only reason this move might have been considered but I would not be so sure this is not an influencing factor. Australia has been the most high profile investigation into child abuse anywhere so far and the WTS did not look good. I think restitution for victims is a real possibility and although the WTS is a master in prolonging legal matters, I don't think they could afford to be seen to be highly resistive to this for a long time. There is also the impact on the local Witnesses to consider. Finally this could spark some serious questions about the tax status of the WTS in Australia.
Whilst all of this is a long time off in terms of legal requirements, the WTS were very quick to act when in dispute with the French authorities over tax. They shifted everything virtually overnight to the UK. We also see large amounts of money going between branches already. I spoke to a sister back in December who worked until the middle of last year in the accounts department in NY and she was quite open about the way the organisation moves funds between all sorts of organisations to reduce legal exposure.
Time will tell on the precise details but I see nothing in the premise of the OP that would be out of harmony with anything else that is going on in JW land.