#1 PE-2 - Would add a Russian attack capability. They are the only major faction without an attacker. I believe it has the largest production numbers of any aircraft not already included in Aces High.
No, I believe that title belongs to the Polikarpov(sumthin like that) U-2, weiging in with around fourty thousand built. Very low priority, as we have no use for nuisance tactics. I believe the only thing it really had going for it versus metal monoplanes was that it was so slow pilots could not pull a bead on their target before they had overshot it.
The Russians have an attack aircraft. Several, actually. The Boston, IL2, La7, Yak-9T...