Hi There. With due respect and without prejudice to what I believe is great fundamental principles. I think there is a sincere oversight in your video about replacing pit toilets. There is one major item missing.
Modern sanitary relies on water and waterbourne means of reticulating effluant. Therefore you need water coming in and water going out.
Problem. If there was a water bourne waste supply there would not be a pit toilet in the first place. So you need a water tank to be filled up regularly. For 12 toilets and water wise flushing systems to be flushed realistically at least 10 times a day you are looking at almost 500 litres of water. Thats 3500 litres a week.
You also cant reticulate that much water into an existing pit toilet desugn as your video implies.
The above appears to nessitate either a chemical toilet system (that the current goverment cannot maintain) or a french drain that will substantially alter your proposed costs. Secondly you would need to utilize about a third of the container as a water storage tank. Water can then be also filled up from rain in areas where rainfall is sufficient to be a resource. In other qreas weekly water would need to be delivered or connected?
Would it not be prudent to start the venture by making safe the existing pit toilet and then roll out your plan (with the required adjustments) as a secondary phase? Costs would most likely be significantly more than your video appears to suggest, but still majorly less than goverments nonscence?
It is of course possible that I am misconstrued and that you have costed a more detailed project than implied in your video, but I just felt like sharing my concern here.