The design discussion turns from simply adding guns to whether they can be placed where they can actually bear. Warships have finite deck space, and a mount shifted for a better forward arc may lose the ability to cover another direction. A nominally powerful anti-aircraft battery is only as useful as its unobstructed arcs and practical mounting positions. The trade-off explains why real destroyers cannot carry every weapon that looks desirable on paper.
Notable Point · 2:32:38-2:33:59
Destroyer air defence is limited by space and arcs
Adding anti-aircraft weapons to a destroyer means choosing between more mounts, usable firing arcs, and the limited room available on deck.