A preference for more defensive layers runs into the limits of Mogami's intended light-frigate role. Adding every desirable weapon would enlarge the design beyond that role. Mogami has to meet a defined set of missions within a cost limit, and its general-purpose equipment offers broad peacetime utility on a manageable budget. In war, the ship joins a task group where other vessels complement its capabilities. This division of labour explains why an attractive additional weapon is not automatically a sound requirement for the design.
Notable Point · 6:19-7:03
Keeping extra weapons within the light-frigate mission
The wish for more defensive layers becomes a design tradeoff: added equipment must fit the cost and mission of a ship intended to supply affordable escort numbers.