Earlier quoted context omitted.
"The only field I can see which will depend on low-skilled worker armies is construction." The trend in construction for the past decade has been towards less labour intensity. So no good news here either.
Construction is already beyond the big wins in labor force though. Construction sites used to have armies of workers. Hundreds. Now they have perhaps a dozen for large skyscrapers, 5 for normal skyscrapers and one or two for houses.
If houses were to move to a prefab model with e.g. plastic construction and standardised room sizes and plumbing and electrical connections between the rooms most of these skilled workers would find themselves redundant...
Fortunately the UK insurance industry inadvertently protects the building industry by making it difficult to insure so called 'non-traditional' constructions.