Good idea on the artillery!
Those Beer & Pretzel rules are actually pretty darned good.... the slang tag line does it an injustice. It would be a good way to break into trying these puppies out.
Another one you might want to consider are the Flames of War, Great War rules....
Great War Design Notes
World War One Battles of 1918
1918 saw great changes in the warfare of the Western Front. Russia pulled out of the war, freeing thousands more German troops to push the Allies back huge distances. The Allied counteroffensives, with the new tanks, evolving tactics, and the arrival of the Americans, forced the Germans back towards their own borders and defeat.
Last year Battlefront marked the centenary of the start of World War One by releasing a set of rules for British and German forces, with issue #324 of Wargames Illustrated. Now those rules have been expanded to a 72-page book, including the Americans and French. Great War writer Wayne Turner shares his design notes, telling you exactly what you can expect to find in this latest edition.
I think it could translate to 3mm with some tweaking....same as I am doing with the Modern rules for 6mm.