A universal 5.5-inch secondary battery

Could the 6-inch and 4.7-inch batteries be replaced with one universal armament?

Yes; a twin 5.5-inch battery could provide more dual-purpose barrels, though each would be less specialized.

Ten twin 5.5-inch mounts, arranged five per side with three low and two high, could form a unified battery. The calibre is linked to a battery considered for Hood. It would give twenty barrels available for anti-aircraft fire in place of six 4.7-inch guns, and twenty for surface defence in place of sixteen 6-inch guns. Each weapon would be less specialized in either role, but the proposed arrangement would provide more barrels able to engage either threat.