Why a supertanker is not a fast carrier conversion

How difficult would it be to convert a supertanker into an aircraft carrier?

A conventional carrier conversion would be very difficult because of speed, though a helicopter or F-35B-style platform is more plausible.

Physical volume does not guarantee aviation performance. A very large tanker offers enough length and deck area to carry aircraft, but its machinery and hull form do not provide conventional-carrier speed. Rebuilding the ship to achieve that speed would be the difficult part of the conversion, beyond laying a flight deck over the existing volume. A helicopter carrier is much more plausible, and an F-35B platform could exploit the long deck for rolling or short take-offs without demanding catapult-carrier performance. The conversion works only when the aviation concept accepts the tanker's original limitations.