On the Engine they had in 1940? It's all extra weight - plus you'll need to add a radio I guess? Going to be an asthmatic dog at Angels 20 where the action is happening
It would have been a 'Boulton Paul Defiant' style one trick pony in a Battle Of Britain type environment.
Specification of A6M2 Navy Type 0 Carrier Fighter Model 21:
Performance: Maximum speed 331 mph at 14,930 feet. Cruising speed 207 mph. Initial climb rate 4517 feet per minute. Climb to 19,685 feet in 7 minutes 27 seconds, 2642 feet per minute Service ceiling 32,810 feet.
Weights: 3704 pounds empty, 5313 pounds loaded, 6164 pounds maximum.
The A6M5a with the structure upgrades was 4167 pounds empty, 6047 pounds loaded, still a ton lighter than the Spitfire MkII
NK1F Sakae 21, rated at 1130 hp for takeoff, 1100 hp at 9350 feet, 980 hp at 19,685 feet.
Performance: Maximum speed 348 mph at 19,685 feet. Cruising speed 230 mph. Climb to 19.685 feet in 7 minutes 1 second. The improvement in the 1943 blower section was somewhat offset by the lower fuel quality
Radios were pulled by some crews for even lighter weight. That won't be happening with the Zero in German service, they understood the advantages of communications better than the IJN
Aeroplane Spitfire Mark II No. P.7280
Engines 1090/1135 Rated B.H.P at Rated Altitude 13,500 ft.
1140 Maximum B.H.P. at Rated Altitude 14,750 ft.
Weight light 4541
Flying weight on trials 6172 lb.
Top Speed M.P.H.
351
Time To Climb to 20,000
7.0 Minutes
Rate of Climb to 20,000
2175 Ft./Min.
TL;DR
A heavier, better built Zero was still going to be just as dangerous, but 'only' 1300 mile range. They wouldn't be able to fly over the Faroes any longer.