Biplanes... hmmn..
...the Hs123, used as a Stuka before the Ju87 came along, andmuch involved in close support of troops for as long as they could be kept flying. They were so useful there were calls for them to be put back into production even as late as 1943 IIRC.
..the Swordfish or "Stringbag", famous for attacks on the Bismark (and the Italian fleet, I think?)
...the Gladiator, famed for its part in the defence of Malta
.. Fiat CR42 - whilst only the one prototype version had a top speed over 300mph, it was nevertheless a fast agile biplane fighter. A few flew in the Battle of Britain escorting Italian bombers, but the Italian units were such easy meat to the RAF that they were soon withdrawn. Whether this was due to equipment or pilot experience I do not know.
...Polikarpov (Po2?), the kukuruznik ("corn-cutter) -used for night harassment attacks against the German Army, and one of the Russians most hated (by the Germans) weapons of war
As for other early war planes, I wonder whether the potential popularity of the Mosca/Rata would be affected if the fighter pilots here knew that the cannons used in cannon-armed variants had such a rapid rate of fire that it packed by far the heaviest punch from a 3-second burst of any fighter in the world well into WW2? Howsabout the biplane fighter that followed the Mosca into production and replaced it in the Chinese theatre?
A few well-chosen early war planes and AH could cover not just WW2 but also the Spanish Civil War. :-)
And, yes I'd fly biplanes in the MA, if we had them to fly.
Esme