This is great
Btw, Can these supporting battalions be assigned to the 5 brigades? The slots for the supporting units are not enough as you mentioned but IMO the slots for the infantry and armored battalions are too many.
I agree with franc001sher, too many combat battalion slots and not enough support battalion slots. Maybe you could make a Column for Artillery only so we can choose how many Artillery battalions a division has and what their type is: light, heavy, ...
For example:
a french (type A) Infantry Division: 3 light artillery battalions and 2 heavy artillery battalions
an Italian Infantry Division : 2 light artillery battalions and 1 heavy artillery battalion
an US Infantry Division: 3 light artillery battalions and 1 heavy artillery battalion
a Soviet Infantry Division: 2 light artillery battalions and 3 heavy artillery battalions
(
source)
Yes, the differences are small. But there is still more variation than for the number of Infantry battalions.
This would increase the customization choices for the Player, because Artillery was the main "damage dealer" on the battlefield (AFAIK).
And it would also allow to better adapt the number of guns in a division to the industrial capacity of a country and to the focus of its leader, quality or quantity (of divisions).