FWIIW, the Wildcat first flew in September 1937 and entered US Services in December 1940 and was designed from scratch as a naval fighter. The Fairey Fulmar, Using the existing P4/34 aircraft as a starting point first flew on 13 January 1937 at Fairey Aviation's Great West Aerodrome. Specification O.8/38 for the Fulmar fighter was issued and an order for 127 production aircraft was placed in mid-1938. Fairey were able to have the first example flying from Ringway near Manchester on 4 January 1940. It entered squadron service with the FAA in September 1940. By using an existing airframe, the P4/34, the development of the Fulmar was much quicker than the norm. The P4/34 was no more or less of a carrier aircraft design than the Defiant. The Boulton and Paul Defiant P.82 prototype (K8310) was rolled out in August 1937 without its turret. The prototype first flew on 11 August 1937. If You take the same time line as the Fulmar and apply it to the Defiant then it is not an unreasonable supposition to suggest that a Naval single seat Defiant could have been available by September 1940, especially as Boulton and Paul had already completed the design study for the P85 naval turret fighter as an alternative to the Blackburn Roc. This adaption is also helped by the design studies already made for the two prototypes of the Bolton and Paul F37/35 to contract no; 556966/36 for but this was later cancelled. There were to design prepared for F37/35, the P88A being a radial engine version and the P88B being a Merlin engined version. With so much preliminary work completed on both a naval version of the Defiant and a four cannon fighter then an amalgamation on the lines used to produce both the Beufighter (Specification F.11/37, First flight 17 July 1939, Introduction 27 July 1940) by Bristols and the Fulmar by Fairey is not an impossible what if time line.