For the basegame, I would welcome more accurate load capacities of allied shipping. The current ones are a bit generous to say the least. The shortages the allies experienced in 1942-43 are not reflected very well.
Viewed from an historic perspective, certain terrain, Burma, Papua New Guinea inland, North Pacific, is too well suited for large scale military operations. Maybe something can be done, increased wear and tear, disruption, fatigue, supply loss.
A large-scale project is out of the question probably, but if it would be done, a game with current level of details on a 3D triangular globe called world war 2 would be nice.