I think a
garden pool system may be a good way of repurposing the swimming pool and easing the owners into other permaculturey ideas. A foot in the door technique!
Here are two videos showing what a garden pool is and what they look like inside:
A garden pool combines poultry, fish, and hydroponic vegetable systems together with an aboveground greenhouse and solar panels if you want to. Waste is recycled in the system to produce food.
They have
free online classes,
do-it-yourself project guides, and convenient
links to building and maintenance supplies.
This image gives a general overview of the workings of a garden pool:
The only thing that isn't free with them is the most crucial part, a the
complete guide to making a garden pool system. However, with the pieces the freebies they show online and the diagram above, I think a garden pool system could be pieced together without buying the guide.