which divisions existed historically with 4 brigades ? Would 3 columns of 4 in the division designer be sufficient ?
Triangular divisions had three (3) regiments. Italians were binary with two. Some early war nations (US, Japan) had square divisions which in theory had four.
Problem is there is no benefit from being strict about a regimental organization. There were some mods in the past that tried to enforce regimental units being in one column.
The other issue is units that are attached to the division. We can only add the battalion to the division. We can't break it down into companies attached to the regiments.
I have yet to find a historical division I can't fit into a 4x4 division grid, even after the inclusion of new units, like combat engineers. Soviet Artillery regiments and Soviet Mortar bn's. Actually there is one exception, the early years square divisions of the US, I ran out of battalion slots. But they get converted to triangular's before a shooting war, so its ok.