Sounds like you've got a great plan for your above-ground pool and irrigation cistern! I love the idea of using Moringa and Neem to keep the water clean and clear. I also like the idea of using solar energy to heat the water. A suggestion for keeping the cistern and pool area clean would be to consider a residential pressure washing service like this
https://sparklewash.com/residential-pressure-washing/ every once in a while. It's an easy way to keep the area looking great and ensure the longevity of your cistern and pool. Keep us updated on your progress!