What an interesting problem, vandalism and poor quality tanks.
I have done a bit of looking around and I see that some of the plastic tanks are rubbish compared with what I see in Australia.
I understand why, no regulations.
I can see why your idea of banding is worthwhile. I have seen it on high pressure timber pipes made before steel pipes were available.
The tightness / spacing of the bands changed for the water pressure involved.
I think your idea of banding, perhaps with fencing wire and 'gripples' that allow fencing wire to be joined and tensioned would be a good idea, low tech high outcome..
Special tensioning tools are available also.
If that technology is not available, old fence tensioning tools may be available.
And using the special fencing knots it will work.
Then on the outside again, lay adobe bricks made from the soil and often used in Africa, which are air dried and then laid around the tank as a protective wall,
set on stone / rubble foundation ring.
Then the exterior is earth plastered using traditional techniques also well know in parts of Africa.
I would like to see more examples of the efforts.
