Hi,
the flight datas of the brewster are not that bad at all. Thjough it dont had to offer much vs the A6M2, but same count for the I-16 and I-153.
The US F2A-3 dont had a more bad performence than the F4F. The F2A-3 got flown by poorly trained pilots in the pacific, the F4F´s got same bloody noses until the pilots got trained to make teamfight.
The FAF B.239 was more light but had less power, therfore the Vmax was worse, the climb similar but the turn better.
I dont see a reason not to include it. The relation between the F2A-3 and the Zero wouldnt be more bad than the FW190A8 vs other 1944 allied planes. The B.239 vs I-16 would be much more close.
I-16, I-153, Lagg3, Mig-3, Ki-43( 1+2+3) and Bf109E-7b are also welcome on my side.

Greetings, Knegel