I agree with Franky when he says the additions to the Il-2 CloD line should be
scenario-based. The often "disconnected" way of choosing additions to the planepool we saw in the original Il-2 line was something I did not like one bit. For me it brought nothing but disappointment, frustration and it did blow up my installation with a load of hangar queens which I rarely used at all.
At the moment I hope for three aircraft to be included: Bf 109 E-1, Bf 109 E-4 and Ju 52 3m (as baronWastelan pointed out - how could I have missed that type?). All three would have significant impact on gameplay (or in the latter case would simply be a much needed addition).
But to be honest I would postpone all three (or any others, for that matter) for significant additions to the game engine in the gameplay aspect. Maddox Games does not only need to fix the many large and small issues of the engine but also fix the FMB (right now I can't use certain objects without encountering almost-CTDs), add a campaign module that is worth the title (with rank structure, medals, roster etc) and - I mean we're all dreaming here - a really good dynamic campaign module that doesn't want to be a strategy game but follows the line of the classic Red Baron II campaign system (or, of newer date, RoF). It would need to be flexible enough to be able to depict very different theaters with very different styles of air war (East & early North Africa vs West & late MTO), really puts the air forces into the role they really played and doesn't force the player to be both pilot and warlord.
EDIT: Franky it's just
Bf 109 E-7. Only E-1, E-3 and E-4 featured the suffix
/b when they were modified for carrying bombs. The E-7 is just the factory standard which incorporated all those changes.