Currently Aces High has two multi-role airframes in the game, but between the two of them there are only three models. I would like to see both families extended to better represent the variety and duration of their service in WWII.
For the Ju88, I would like to see it updated to Aces High 2 standards and for three additional Ju88 or Ju88 based aircraft to be added. All of them would retain the Ju88's robust airframe while bringing other aspects of the Ju88's capabilities to the game.
Ju88C-6: An early Ju88 fighter armed with MG/FF 20mm cannons.
Ju88G-7: A later Ju88 fighter with much higher performance, armed with MG151/20s, and sometimes with a Schrage Musik installation.
Ju188A-1: A substantially improved bomber developed from the Ju88, carrying the same bombload as the Ju88A-4, but much faster and better defended.
For the Mosquito we don't have to worry about an update, but there are several additional versions which would add nicely to the game.
Mosquito F.Mk II: This would not need a new 3D model, the Mk VI's model being visually the same, would be the early Mosquito fighter with lower performance due to Merlin 21 engines, no bombs and a weaker wing than the Mk VI.
Mosquito B.Mk IV: This is the early war Mosquito bomber. It is slower than the Mk XVI and can only carry four 250lb or four 500lb bombs. Like the Mk II it has an earlier wing that is not as strong as the wing introduced on the Mk VI.
Mosquito NF.Mk 30: This is the ultimate Mosquito fighter of the war and while it is slower down low than the Mk VI, it is much, much faster at altitude. It lacks a bomb bay, being limited to two 500lb bombs or two drop tanks on the wings. The four .303s are omitted in favor of a bull nose with radar (not asking for avionics to be modeled) instead. While it was a night fighter, it also saw use during daylight operations on many occasions.
Adding these aircraft would give a better feeling as to why these two airframes stood out as different in a time when very few airframes proved to be capable of being effective multi-role units.
Also, being able to recreate one of the dogfights between escorting Mosquito FB.Mk VIs and defending Ju88 fighters sounds like a lot of fun to me. It is the only place I can think of where dogfights happened between big twin engined fighters without interference from their smaller, more agile single engined brethren.