There was an enormous growth in artillery during that periode. At first Artillery regiment were just administrative units with the individual batteries assigned to brigades or divisions.
Larger Artillery units started to appear around the American civil war with Lee creating artillery battalions of 16 guns in the ANV.
The Union had light artillery and heavy artillery regiments but they appear to have operated largely as independant batteries assigned indivudually to the infantry or cavalry brigades, except for whole units left in a fortress. Though I am not sure for the later stages of the war.
In the Prussian army each corps had a field artillery regiment which operated as a body during campaigns. In the larger battles, the artillery regiments of several corps were often grouped together resulting in concentrations of several hundred guns.
Then between 1870 and WWI artillery kept growing. Divisions recieved one or two field artillery regiments operating as one body with heavy artillery regiments at corps and army level.With trench warfare heavy and siege artillery regiments were grouped into temporary artillery divisions to support offensives usually at army level.
The allies were slower in their move to organise larger artillery formations. The British entered the war with their batteries acting individually in the old napoleonic way.
The allies tried to break the trench deadlock by piling more and always heavier guns. Artillery doctrines also showed a large evolution during WWI. The allies believed in the long artillery preparation lasting weeks before the offensive while the Germans used the hurricane barrage approach which was a short and violent barrage just before the offensive.
The techniques of the artillery barrages also evolved from the mere pounding of the enemy positions to more advanced barrages. Again I think Lee was one of Pioneers IIRC as he used an artillery barrage to isolate seminary ridge and prevent reinforcements from coming.
In WWI those were refined Creeping barrage, boxing barrages gas bombardments........ The development of communication and observation techniques telephone, radios, aircraft, also hade a great effect.
To represent that in game field guns should be factored out in the divisions like in HOI with technical advances and doctrines improving the stats of the units. In addition to that there should be independant artillery units representing siege trains wich should be very expensive an slow moving.
Then around the technological of WWI and the advent of Trench warfare heavy artillery units should become available