Back to the OP, my money would be on a Defiant conversion. It has wide track undercarriage for starters - which would be a massive advantage for carrier operation - and the removal of the hefty turret with drag reduction would offset the retained weight of the extra crewman. It should also provide space for kit The P.94 derivative proposal with 12 .303s had a reasonably predicted top speed of circa 360mph. Lets chop a good lump off of that because of the FAAs obsession with filling airframes with equipment (with the obvious necessities like an arrestor hook, long range radio, decent dingy etc) - but a 330 mph aircraft is surely still a reasonable proposition? ... its also an aircraft in production - and the proposed P85 turreted naval variant of the Defiant may have already covered off some of the other required design mods for arrestor hook installation etc.
However, its still a Merlin engine - and regardless of rating, as others have said, its going to deliver its best performance at higher altitude, not low down as per the Fulmar spec. However, even a Defiant *with* its turret looks to have had a better climb rate than the Fulmar, so perhaps a faster climbing P.94 would have the advantage of being able to convert altitude into speed. Its mentioned in several passages I've read that Fulmars on interception often only had a chance to attack head on in a single pass or by diving onto things like JU88s if they had an altitude advantage.
And please give the poor old Nav Op a decent weapon to defend the tail. Perhaps a good fast firing gun like a VGO in a double Hampden style mounting?