How would Taranto have changed if the British had committed another carrier's resources to the strike?
Short answerTaranto already formed part of a multi-carrier plan; combining Ark Royal with Illustrious could have greatly increased the striking force and the damage to the Italian fleet.
NotesTaranto belonged to a wider, multi-carrier operational plan. Illustrious and Eagle were intended to attack from the eastern Mediterranean while Ark Royal covered a convoy and struck Genoa and other targets. Concentrating Ark Royal with Illustrious could have added Skua dive bombers and perhaps tripled the available Swordfish. In this counterfactual, the larger torpedo force could have inflicted damage from which far fewer Italian ships would return quickly.