So in game (and table top, I assume) we have: Spearmen, Spearmen with Shields, Swordsmen, Halberdiers, and Greatswords.
What sort of uses do all these units have as it seems like a lot of variety for nothing. In reality the time period Warhammer fantasy is analogous to relied on pikemen and gunners to form the brunt of the army, with cavalry on the side and cannons to rule the field. Knights were being quickly phased out and aside from pike and shot formations you might have some irregulars with swords (but no shields) to hack away at enemy formations when opposing pikes met. Now obviously this is a fantasy setting and the arrival of advanced blackpowder weaponry has (for some reason) not phased out older methods of warfare, especially since we have all sorts of other races with varying degrees of technology who are all extremely relevant with their martial strength. I'll cede that.
What I don't get is how, within one's own faction, you have redundant units. It is my understanding that in the lore The Empire has pike units much like Estalia and Tilea. They have gunners. Short spearmen are already rendered obsolete. Spearmen with shields are definitely rendered obsolete. Swordsmen with shields I'm not sure about. The real world reformations are based on the fact you're fighting Humans vs Humans, using the same sorts of military strategies and advancements. So it was pike and shot vs pike and shot. That isn't the case in this fantasy setting. Do the swordsmen fill any sort of purpose in this setting that isn't relevant in the real world equivilant? If it is for flanking then it would seem Greatswords do a better job of that, especially against some of the more physically imposing races of the world. Now Greatswords and Halberdiers would have been used to push the pikes in the real world. When two opposing pike formations met and the pikes created a "no man's land" as they jostled for advancement the greatswords OR halberds would hack at the pikes and opposing infantry as they got closer. They kind of had the same purpose, just different flavours by different countries. Seems like you don't need to have both.
So that's all fine for reality, but Warhammer isn't reality. Am I trying too hard to make sense of it all?
Doesn't help that we're told in the lore the Empire uses Pike infantry, but in the game and the tabletop they do not have Pike units which throws this all out the window. If that's the case then what unit should be the frontline, core unit and what purpose do the rest of the infantry have other than for player variety? I've seen mostly Halberds in state troop artwork and miniatures.