It's funny you should say that! I've considered if there would be a Scramble for Australia, similar to Africa. Many of the nations in Europe wanted part of Australia, and I wondered how that would have worked

Ok, so I've had some time to consider points of divergence here. The first and obvious one to consider is possibly with the German victory in the Great War. Oddly, it seems Germany wanted to expand into Africa, not into a region that had a large pro-British population. What we can consider is the economic ramifications of the British Empire losing the Great War, taxing their colonies, and seeing those colonies demand greater autonomy for it. That's at least the approach I had for India. The other concern is taxes were no longer collected from Australia since 1855, and then it was federalized in 1901, so that approach wouldn't work.   The POD could be, like you said, the GEACPS. However, Japan is not allowed to expand its territory through annexation due to the terms of their treaty, and Australia could be too culturally different to fit in the GEACPS. That doesn't mean it's not a threat to Japan. If anything, Australia is the only nation keeping Japan from pure dominance in the Pacific. Yeah, Germany has Papua New Guinea from Britain, but they also have been turning a blind eye to Japan since the Russo-German War. I could see an alternate Pearl Harbor being an attack by Australia on Japan.

That would be interesting, although it would be later than most of the rest of the timeline.   Looking at the nations of Australasia, I run into a few places that raise questions - What's going on with Samoa? Or French Polynesia? Vanuatu?

It wouldn't be too much later, probably the 1940's or so is when we'd see that huge rivalry between Japan and Australia. It is a bit farther than where a lot is developed, I'll give you that.   With Samoa, there's an interesting claim that Germany was very popular there, and so it remaining a colony of Germany is likely for the time being.   French Polynesia, without a French colonizer, probably goes to Germany or Britain.   Tyrdal asked me about Vanuatu, and, unfortunately, I couldn't think of any reason why it wouldn't go similarly to our timeline.

I would love to see things advance towards the 40s, so building out the Pacific nations to that point would be interesting!

The frustrating part is that a lot of these island nations in the region would primarily be military bases for the global powers in order to strike at each other. Beyond that, there's not a lot of divergence from their Colonial history that could be played with. There's Papua New Guinea, Australia, and New Zealand, the former is still a colony, while the latter two would barely be operating independently. Australia could declare itself a Republic if it feels Great Britain isn't doing enough for national security in order to take matters into its own hands, but doesn't have the population needed to stand against the GEACPS by itself.

What if the Japanese supported the Māori Kīngitanga movement with the goal of creating a native Māori kingdom on New Zealand that would join the GEACPS and be a Japanese ally rather than a colonial territory?

Added Australia to the world!  

Yay!

It's short, but I can always add on to it