Why adding EMALS would be more than a catapult refit

Could the Queen Elizabeth-class carriers receive EMALS in a mid-life refit?

Technically possible, but only through a costly change to the ships' aviation concept, structure, aircraft, and recovery systems.

Steam catapults do not match a gas-turbine carrier without adding steam-generation machinery, so the realistic launch option would be electromagnetic. EMALS was still technically risky when the British decision was being made, and the government was reluctant to make the carrier depend on an immature system. A later conversion would also mean moving away from STOVL aircraft and adding arresting gear, recovery systems, and extensive internal changes. Any proposal would need a new aircraft or uncrewed capability valuable enough to justify the entire conversion. EMALS cannot be treated as an isolated upgrade.