Well, IRL heavy fighters were a dead concept apart from the night role. The adoption of drop tanks along with more internal fuel combined with the logistical simplicity of 1 engine, 1 crew member, SE fighters gaining significant horsepower, and sufficient firepower ended the romance some nation's had with heavy fighters.
A heavy fighter shouldn't be equated with a 2-engine fighter. Two engines were used because powerful enough engines weren't yet available, just like in the past passenger jets needed 3 or 4 engines, but nowadays the B777 is huge and requires only two engines because they are much more powerful than previously available ones. The 1936 models, sure should be 2-engine fighters and quite bad, but IMHO the P-47 should be the 1944 tech Heavy Fighter for the USA. It was significantly heavier than other fighters of the same time.
en.wikipedia.org
Empty Weight: 4.5 tons
Range: 1,030 mi (1,660 km, 900 nmi)
Role Fighter-bomber
en.wikipedia.org
Empty Weight: 3.2 tons
Range: 900–1,000 km (560–620 mi, 490–540 nmi)
Role: Fighter
en.wikipedia.org
Empty weight: 2.2 tons
The heavy fighter 1944 should be this: Similar to a fighter in performance, but costing more and with a greater range and with a small hability to bomb logistics and ground troops. Heavy fighters should be fighter-bombers.
en.wikipedia.org
The P-47 was twice as heavy and had four times the fuselage size of a Spitfire. Armed with eight .50 in (12.7 mm)
M2 Browning machine guns it could outshoot any enemy fighter,
[32] and as a fighter-bomber, it could carry half the bomb load of a
Boeing B-17 Flying Fortress or 10 five-inch (127 mm)
High-Velocity Aircraft Rockets.
Seriously, half the load of a B-17 is a lot and therefore it another proof it should be classified as a Heavy Fighter, not a light one.
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