How much stronger would Malta's Force K have been with Renown or another heavy-gun ship?
Short answerMuch stronger, because a battlecruiser or heavy cruiser would add decisive striking power, but the Royal Navy could not readily spare such a ship.
NotesThe counterfactual begins with the original Force K fighting Italy while Renown works with Warspite. Extending the idea to Malta, a battlecruiser or even an eight-inch-gun cruiser would have made the raiding force much more dangerous. The existing light force already achieved substantial results against Axis traffic. Ship shortages and competing demands kept such a major unit from being based there.