As mentioned before, I am really interested in how Project H is going to redesign the Hippo Roller. Looks like they have been doing some user testing and figured out they have to go back to the drawing board.
Some ideas that caught my eye, were localized manufacture and using alternative parts. That said, designing for severe conditions where skilled people are scarce if a product needs repairs, it would be better to minimize the amount of moving parts and simplify the product and its manufacture.
In order for this product to be accepted by people, lowering barriers such as cost and ease of use are critical. Just looking at how difficult it is to pull the roller up a relatively even slope and pouring seems to me that weight and size are the biggest issues here. Perhaps it would be a good idea to determine exactly how much water a family needs, how often they need it and what is the actual value a Hippo Roller delivers versus the difficulty of using it.