Keep the generic IC attached to pronvinces, but add an allocation feature. Split the total IC into different categories, for instance:
Air, Naval, Vehicle, Munitions, Supplies (food, clothing, fuel production, anything not covered by the other four)
Each is assigned a percentage by the player of the total IC. Changing these percentages causes a retooling penalty that lowers overall IC production for a period of time (retooling penalty and duration can be reduced through research, government type or nationality).
Each brigade/unit type in the game is made up of these 5 resource or production types. For instance, a tank brigade may consist of 70/20/10 Veh/Mun/Sup. Production time can be affected by the percentage of IC devoted to these types and how important they are for that particular brigade. Overall division production is affected by the production times of its individual brigades.
You can change the production/resource types, but the connection to unit makeup is the key. Whatever mix you come up with, production time should depend what types are being emphasized and what percentage of that type constitutes the unit. That way one can truly focus their industry on a particular unit type.
Notice that munitions and supplies/other should make up a portion of every unit. So, while their percentages per unit may be smaller, they are part of everything and remain very important (EDIT: and constitute the bulk of infantry units).
Also, create a research area for industry that not only allows for retooling efficiency, but allows the player to further focus their war efforts toward a particular field. Allow research to give production bonuses and improve the resulting equipment.