I spent about 5 years in Alice Springs in the 70's so I have an affinity for you blokes Down Under!
Here are a few thoughts regarding your project:
1) Here in the States, we are over regulated and paranoid about safety. We have come to expect any job to be over-engineered and complex, or it won't work. We have come to fear even the smallest risk to our health and spend excessively to reduce that risk. It sounds like you don't have these burdens.
2) How will you design and build a cover for the pool? I imagine a solid concrete, reinforced slab over the pool; but then again, see #1 above ;) I'm sure there is a simpler way.
3) Can you capture enough rainwater to supply your needs? Your roof is the obvious choice, and any other source may add to the filter burden.
4) I saw the TOH episodes in Bermuda. The whole community was served by rainwater caught in basins acres and acres large. It goes to show that catching and storing rainwater is a feasible method on any scale. It sounds like you can supplemant your rainwater with well water if needed. You will have to tie both plumbing systems together somehow.
Good luck with the project,