Could 4.5-inch guns have prolonged Vanguard's service?

Would Vanguard have been better or worse with 4.5-inch secondary guns?

Combat capability would change little, but commonality could support training, trials and a longer reserve life.

The initial assessment is that 4.5-inch weapons would make little difference to Vanguard's overall fighting power. Commonality with other ships could make her useful for gunnery training and trials of automatic mounts. Some positions might be retained for training while others tested new equipment, allowing a smaller reserve crew to support the role. Fire-control improvements could be shared without adapting calculations to another projectile. A longer life and possible later operational use are suggestions in this counterfactual, not an approved retention plan.