More versions of airplanes, it may seem stupid, but I would love to see the F4F-3, the F6F-3 and a late war version of the 109G-6. There was a reason why the G-6 was flown until into the later parts of the war.
Fixes to the FW190A-8 would be nice as well, it's too heavy and was 'supposed' to be more nimble than the A-5, according to encounter reports.
Variations of ammunition loadout, for example, the .50 cal API round(armor piercing incendiary) was not available to everybody at all times. P-47 encounter reports sometimes list ammo usage and they would list the two kinds of ammo load they had, Armor piercing and incendiary were separate and split between the four sets of guns. Maybe even adding a 20mm option to the Stuka.
The LaGG-3, Ki-43, J2M/5, Ki-27, MiG 3, 109F-2. Ki-84-Ib/c, A-26, I-153, I-185, Pe-2/3, P-63, All the different Yaks, too many transport planes to mention, HE-111, Seafury.
In addition, something that has nothing to do with anything above, I would love if the killer of any perk plane received a percentage of the perk points used to purchase the plane. If a p-40 shoots down a 262, don't you think that deserves 40 perk points? I never use em, they're mostly useless to me, I'd give em away if I could - but I do like seeing that big number at the end of a good sortie.