Britain could answer Plan Z while Germany was still building

How serious a threat would Plan Z have posed to the Royal Navy?

Britain would react as German ships were laid down and could probably complete its counters first because its maritime industry was broader and deeper.

Britain could respond to German capital ships as they were laid down, using a broader and deeper maritime industry to build counters that might be ready first. In this interpretation, the Treaty of Versailles deliberately weakened German maritime infrastructure, leaving Germany far below its pre-1914 base. Even before the First World War, German risk-fleet theory sought enough strength to make a British victory prohibitively expensive. It assumed that losses against Germany would expose Britain to attacks by other powers, an assumption questioned here. British numerical superiority helped limit that risk, while concern about a desperate German attack influenced naval planning. The later Anglo-German Naval Agreement capped German strength at a proportion of Britain's and tied Germany into the wider treaty system. Foreign constructors could detect implausible displacement claims, so evading treaty limits still required a believable public account of a ship's size.