I don't think it's inappropriate for "Zero" units to call artillery. Training to do so is standard and can be found in US Army field manuals at platoon level. I've done so myself, but only in training. We did call in live rounds, however. Way cool!! Not sure if they 86 it when it hits real combat situations, however.
As far as artillery target patterns (sheafs), that might be something we would want to take over to the Blitz forum. Nothing in the game restricts anything you've suggested. Below is a link that discusses more about artillery sheafs.
http://www.poeland.com/tanks/artillery/sheafs.html