The economic model of A&A is a extremely simple, with only 1 type of resource (IPC's), though constrained by factory production limits. AA50 adds the additional feature of national objectives, where bonus IPC's are awarded for strategic objectives.
TripleA has the capability of supporting multiple resources, but the additional resources will not be shown on the screen.
Many elements could be added to increase realism.
You could add some sort of maintenance rule, to reflect the costs of field operations. The Piece Limits has some of the same effects.
You could add additional resources such as manpower or oil.
You could have a more realistic distribution of income values. The game exaggerates the income of Japan.
National objectives could be used to reflect trade routes.