Which are the unions that will have a lot of power in what is effectively a monopoly shipbuilding industry in this continuous ship build?
I hope they have the national interest at heart, rather than narrow self interest, but to do so would abrogate their raison d'être, unless they take a long term perspective and avoid a future government reversing this continuous "guarantee".
Relying on people given enormous power to not use/abuse that power does not have a good history. Look at CFMEU/BLF/Painters &Dockers/Newspaper Print Union/ etc.