Great docs HP!
Just a though in addition... seems to me the main problem is the lye solution which is not so easy to make without chemicals or hard-wood ash (which will be not available in rural Afghanistan for sure).
Cement is quite alkaline, so maybe there is some way to use it to make lye (in another thread on this board someone was making a porous concrete filter and one of the problems was that the filtered water became quite alkaline).
Another option (more high tech, but with other benefits) would be to take one of those electric salt separators (I think there are even some solar powered ones now) which produce chlorine solution (for treating drinking water) and as a by product NaOH (which is sodium lye solution) out of water, electricity and table salt (NaCl).
Actually that would be a pretty neat thing to produce the two most important WASH consumables (soap and chlorine) in one go