EA research jobs are often remote, and if there aren't many meetings the timezone difference to an org's headquarters can be pretty manageable. I spent the first month at OP working from Sydney. My team was spread across the US and UK, which did make finding times suitable for everyone trickier. But it was doable. My impression is that Rethink Priorities is similarly flexible wrt location/timezone. Givewell is more restrictive - requiring people to be within 3 hours of Pacific Time.

CE/AIM's incubation program was/is spread across timezones, and if you founded a charity you'd be deciding where to live. While there are advantages to living in hubs of funders/influence, I don't think they're decisive. The issue is whether you'd be able to spend time in the field, but that can vary depending on the intervention and co-founder. 

I think there's a lot of local maxima that are very juicy. I would encourage people to look at the opportunities around them that others would miss, and try my best to foster a culture that helps its members discover them.

A great example of someone doing this is Abdurrahman who took the initiative to create EA in Arabic which I expect will be really impactful. I don't expect there were many EA jobs available to him in Saudi, but he looked around and found a gap (no resources on EA in one of the world's biggest languages) and executed on the opportunity.

I am currently looking into an animal welfare intervention which South American EA's would be much better suited to do than anyone else. Some time ago I looked into policy interventions to improve the water sanitation efforts of the Jal Jeevan Mission in India. An Indian EA from the right state would be much better suited to carry out the sanitation advocacy for JJM than I am.

I've yet to find a region of the world without opportunities, but most of them won't be listed in a career guide!

It can be disheartening for people to be stumble across 80,000 hours content and be inspired but then be left a bit disappointed by the practical options available to them.

To me this is the key point in your post: if you try to bring people into a movement, saying "X is the thing that most needs doing" and then when people decide "ok, I'll go work on X" you say "actually we have a lot of people already, probably go do something else" they will understandably be disappointed!

But I'm also a little confused by your calculations. You say:

If we assume fifty percent of the attendees are interested in EA roles (100) then there is roughly 10x as many people interested in EA roles as there are available domestically.

The 10 roles available in Australia sounds like it's coming from adding up the number of Australians working in EA community building in Australia, is that right? If the number of people in EA community building were on the same scale as the number of people attending EA conferences, that would actually be very worrying -- if people count impact by getting others into the movement, but then the only impact those others have is getting still more people to join the movement you're not actually doing anything to make the world better.

When I look over the 80,000 Hours list of pressing problems I see lots of things that it should be possible to work on from many places, including Australia?

(Aside: I saw you used both "give to earn" and "earn to give". I'm used to seeing the latter -- was this a typo or is there a distinction you're trying to draw between the two?)

Alternative career paths could include things like government policy roles that have say a tenth of the impact of a global hub EA policy role but still are the highest impact opportunities available

I'm not sure policy effectiveness works like this. Perhaps AI policy is particularly concentrated where AI innovation is happening, but I would have thought e.g. animal welfare policy is pretty global, and while bigger markets have more impact, they correspondingly have less tractability / more competition, so the smaller market may be easier to find success in. It's even more complicated than that when you realise that policies can be modelled on success in other countries, so positive change in Australia could be a useful resource for the global effort.

You're definitely not alone in this— we grapple with similar issues here in NZ. 

As others have said, remote work, earning to give, government/policy work, and starting your own project can all be good options.

EA NZ has set up a job board featuring remote + NZ-based roles, which might be useful to you also? (Though obviously the NZ-based jobs are only relevant to kiwis or those wanting to move here).