How much larger would the Fleet Air Arm have been if the Royal Navy obtained the carriers it wanted?
Short answerThe key difference would be many more carriers and therefore a much larger, better-supported Fleet Air Arm, not simply bigger individual ships.
NotesThe Fleet Air Arm would not necessarily become larger because each carrier grew. The greater change would come from the Royal Navy receiving more carriers when it wanted them during the 1920s and 1930s. A larger carrier fleet would create sustained demand for aircraft, personnel, training, and institutional investment. Ship procurement and development of the air arm would reinforce one another across the whole force.