What Vanguard might have changed in the Falklands

Would a retained and rearmed Vanguard have been useful in the Falklands War?

Potentially yes, especially for command and naval gunfire support, but only if her ammunition and maintenance had been sustained beforehand.

The speculation treats Vanguard as more than a gun platform: she could offer staff space, a flagship role, and heavy support for troops ashore. Commodore Michael Clapp's amphibious force lacked generous command facilities, so a large capital ship could have improved coordination as well as firepower. Heavy shells might have suppressed the Stanley airfield or supported troops approaching Argentine positions, though the scenario remains counterfactual. It also notes the practical requirement to sustain ammunition and maintain a usable stockpile before the crisis began.