Firstly, this idea has been in the press a while and if you look back you can see the report. Personally I think it is a possibility that a secondment could happen but it would be in an observer role. Exchanges between countries military, esp. within the Commonwealth, are not unusual. He would not transfer for a combat role - that is impossible because they fly different attack helicopters and training would take in excess of 6 months, which is the period of time mentioned for the entire deployment. So for someone who wishes to remain in the military, at least for the foreseeable future (say 5 years) working with other forces is good for your career. So on military grounds - there isn't an objection.
Secondly, there may be an objection on political grounds - that is possible, but not definite. Australia may at some stage decide to end their constitutional monarchy but I don't think that they would leave the Commonwealth. So working together would still be valid.
Thirdly, whether Harry wanted to do it - be away from the UK for 6 months. I would say probably yes.
And finally, if Australia didn't want him, I think Canada would welcome him with open arms.
These issues are never one dimensional and this sort of story (unlike Harry's love life and the cot for Baby Cambridge) usually has some basis in truth because it is possible.
Six months here will sort him out!
