They already had, which was why they bought the Gladiator which was at the time of the order being made the standard RAF fighter. All this proposal does is change the order to a higher performance aircraft that the RAF has (at that time) decided it doesn't want. Both aircraft need adapting but all in all the change shouldn't delay things by much and the FAA would be much better prepared for Norway and the Mediterranean war in 1940.
The important part of my point was, 'and having a higher priority than land based fighters.'
Crediting Fulmar alone for Axis not sinking more RN carriers is a foly, as it is forgetting how many merchant ships and other warships were sunk that were supposed to be protected by FAA. Foly is also blaming Zero and Wildcat for losses of their respective carriers.
On the other hand, all of the 3 major sea-borne powers failed to field a real peformer of a fighter in 1941-42, despite the technical possibilities available.
I am not crediting the Fulmar, I am pointing out the limitations of a high performance fighter in defence of a high value naval target. Its highly situational ( see USN CAP during the Rabaul raid in early 42) but in term of the primary mission of a CAP over carriers the Fulmar and the Air defence system it operated as part of is much more successful that either the USN or Japanese up to mid 42.
In terms of other ships lost, the main loss of warships is off Crete - no carriers present. Off Enemy coasts, either in the Dunkirk evacuations or on coastal raids vs Libya. One is covered by land based air the other, no carrier. Now that may be an argument for building CVE so you can have aircraft everywhere, but that requires wartime levels of finance and manning.
An earlier decision to have a high performance fighter would have resulted in different production requirements earlier which while maybe not changing the number or even aircraft available in 1939 might effect massive changes to the aircraft used by FAA in 1940 and 1941 and not having to rush development of the Sea Hurricane and subsequantly Seafire when it became apparent that a higher performing fighter was required for ops in a littoral environment vs land based twin / triple engined bombers and modern single engined fighters.
No, the diversion of resources to a third aircraft comes at the expense of something. The early war production run of any new dedicated carrier aircraft comes at the expense of something. The national priority in the period was Air defence of the UK, and after that protection of major bases by ground based aircraft, which is why the priority is also given to AA command over other parts of the ground forces. It is only after that is felt to be completed that production can be diverted to other needs. and with the BoB that means until late 40 at which point the Wildcats are on the way and lend lease is available avoiding the need to develop a dedicated naval fighter in a hurry. The first AtA kill of an F4F is over Scapa in December 40.
That they are not then redeployed to the Med is a command decision and a reasonable one given the difficulty in delivery to the Eastern Med and needs in the North Atlantic.
The argument seems to be that in 1938/9 the UK should prioritise defence of overseas naval assets against neutral Italian aircraft when you hope to keep Italy neutral as opposed to defending London from Luftwaffe bombers dropping chemical weapons on London from bases in Germany. Which they are capable of doing.
To which the answer is build more Spitfires. AA guns Radar Stations, deterrent bombers of your own.