Upping as a fighter would be completely reasonable, since WAS used as a night fighter. If needed, could even make the night fighter version a separate entry with a different model number -- the P-70.
OTOH, the 4x 20mm might be a disappointment for you. It used the US Hispanos (which were manufactured with a chamber size incorrectly converted from the original metric measurements -- I am not making this up). It was very prones to jams unless the ammunition was manually oiled before loading, and (most importantly for AH) only carried 60 rpg in the drum magazines. Thats what the new spit V has, and you can see how popular it is in MA.
In real life, the US was so underwhelmed with the cannon variant that every single airframe was given to the soviets.