The Gloster Gladiator and the Fiat CR.42 would make an interesting addition to the early war plane set.
The Gladiator equipped 13 of the 35 Fighter Command squadrons at the beginning of the war, 2 squadrons served in France and 1 took part during the Battle of Britain. They continued serving in Africa and the Mediterranean until 1941.
The Fiat CR.42 was built from 1939 to 1943 (total of 1781). It fought in various theaters an against the Gladiators in North Africa.
I think it would be interesting to have a biplane vs biplane missions and/or snapshot.