The idea is similar to the 'light fighter' - a fighter aircraft that can be had in short term, without breaking the bank, that does not use spanking new engines the 1st line aircraft depend upon
(number of countries that can get a Merlin or DB 601 in 1939 in any numbers is about one-two for each engine, but Kestrel, Mercury or Jumo 210 were far easier to get to anyone).
Decent firepower, but nothing heavy, say 4 LMGs or 2 HMGs early on, and later a bit more powerful weapon suite.
Resulting fighter is not all-singing all-dancing, but that can improve numbers game for big airforces, while probably being the only type of fighters available for other countries - be it as something they buy abroad, or something they make at home.
(number of countries that can get a Merlin or DB 601 in 1939 in any numbers is about one-two for each engine, but Kestrel, Mercury or Jumo 210 were far easier to get to anyone).
Decent firepower, but nothing heavy, say 4 LMGs or 2 HMGs early on, and later a bit more powerful weapon suite.
Resulting fighter is not all-singing all-dancing, but that can improve numbers game for big airforces, while probably being the only type of fighters available for other countries - be it as something they buy abroad, or something they make at home.