This really would only be of use for buildings with a cavity or void below the ground floor. One of the issues t the moment is water, with an option being a grey water tank. As far as I know these are fairly large and put into the ground near the property. A lot of houses in UK have these suspended lower ground floors. Mine is approximately 140cm and in footage covers the whole footprint of the original 1930s building.

I actually looked at getting one of these tanks but didn't go for it due to the work that would be involved in putting it into my garden etc. If a modular system of tanks was devised that fitted between the joists prior to fitting together or a compressed system that was expanded into an outer 'case' that was put together was in the void.

This would mean less destructive work and the piping could fairly easily redirected.

Another option could be to suspend a modular system between floor joists and could therefore be used in flats. However this obviously has issues due to weight. limited space and the clear problems of bursting or piercing due to 'human error'.

An attic mounted system is also an option but again has issues of weight with reinforcing necessary, plus a reduction in space and having to insulate to prevent winter freeze.