The list so far (with possible aircraft, although we probably need to reduce the list of aircraft in some cases):
Battle of Britain. Britain's finest hour. Spit I's, Hurri I's vs. 109F's, 110C's, He 111's, and Ju 88's.
New Guinea, 1943. Fierce fighting involving Japan's highest-scoring aces. Ki-43, Ki-61, maybe Betty?, P-40, P-38G, B-25.
Channel Dash. The Kriegsmarine is trying to get Scharnhorst, Gneisenau, and Prinz Eugen to safety. The Luftwaffe put up a huge moving CAP over the Channel, and the RAF struck in force. Spit V, Hurri II, Beaufort, Wellington, Swordfish, 109F, 190A-5, 110C, maybe Ju 88.
North Africa. Fights in the desert of North Africa. A very fun plane set and nice change of terrain. Spit V, Spit IX, P-38G, P-40, P-39, A-20, B-25, Boston, 109G, 109F, 190A-5, 110C, C.202, Ju 88.
Late-war 8th AF. 8th AF strategic bombing with high-alt escorts vs. high-alt Luftwaffe. Like DGS/BOG. P-51, P-47, P-38, B-17, B-24, 109G-14, 109K, 190D, maybe some 190A-8.
Cactus Air Force. These guys fought out of Henderson Field on Guadalcanal under very tough conditions and held the place against concerted and repeated Japanese air attacks. This is where Joe Foss fought. A6M2, A6M3, D3A, G4M, F4F, P-39, SBD, TBM.
Battle of the Bismarck Sea. A major engagement in the Guadalcanal Campaign with a good matchup of aircraft. Ki-43, Zero, P-40, P-39, P-38G, A-20, B-25, singleton B-17/B-24.
Battle of the Santa Cruz Islands. A battle between carrier groups. Zero, D3A, B5N, F4F, SBD, TBM.
Late-war Philippines. A fight with late-war Japanese fighters and bombers. Ki-84, N1K1, Ki-61, A6M5b, Ki-67, P-47, P-38, F4U, F6F, B-25, B-24.