I think highlighting the unintended consequences of space standards is an important debate and it goes beyond just buy in. Houses built in recent years should have much lower heating and energy costs than smaller older properties, financially penalising those who can’t afford properties at the top end of the local market.
More research into the size, type, location, and which qualities of housing that promote "happiness and mental wellbeing" should influence housing policy. I am sure a "one size fits all” policy isn’t ideal, but we as a species should be more than capable of improving on what we currently do and at a greater rate than we currently are.
Finally there is still the question about how healthy our obsession with home ownership is? Would we be better off in terms of happiness and mental wellbeing by moving away from property as a tradable commodity? More research in this area could be really insightful.
This must have more potential outside of London where land values are much lower and construction costs make up a bigger proportion of final value. The other thing to note is that the glass roof in the image shown of the OMMX house, would probably push the shell costs above that of complete houses of the same size in a more standard 'spec'. This isn't a problem per se as this is really offering high quality bespoke housing more affordably, but not more affordable housing.