Historically (which seems to be how I start 'way too many of my posts) the 'Great Swordsmen' of the Medieval/Early Modern Era were, in the Middle Ages, mostly long axemen - at least, that's who is usually depicted in the contemporary artwork. Except for the similar English Bill, the Halbard was never a separate weapon in this period (it was in China much, much earlier - Classical Chinese infantry appears to have been almost all Halbardiers and crossbowmen), it was, rather, included with the 'pike blocks' along with 'double pay men' wielding two-handed 'great swords', all to help break up the enemy pikes and help your own pikes forward.
The earliest 'pike and shot' units, the Spanish Colunelas and Tercios, in fact had not only pikes and arquebus/muskets, but also halbardiers and swordsmen.
The Tercio, then the Dutch 'linear' Battalions and the Swedish Squadrons all evolved into 'pure' pike and shot by the early 17th century, and by the end of that century, when the matchlock was replaced by the flintlock, or Fusil, the socket bayonet was adopted at virtually the same time so that the 'musketeers' (Fusiliers) with fixed bayonets could both defend themselves from cavalry and fire fast enough to destroy anything in front of them.
So, from about 1700 CE (very early Industrial/Late Modern Era) there is One infantry type: Fusiliers, the unarmored infantryman carrying a flintlock musket with bayonet. This type of infantry Screams to be included in any 4X Historical game, both because of its importance in cementing Europe's domination of the rest of the world in the 18th and early 19th centuries, but also because it coincided with the most colorful period of military uniforms in world history. Just by reskinning the basic figures, every Faction could have Fusiliers in different colors of coats, waistcoats, collars, cuffs and trousers.
The 'riflemen' so beloved of previous Civ games were a historical footnote: while the Fusil dominated warfare for over 140 years, the black powder rifled musket or breechloading rifle lasted less than 40 years - from about 1850 to 1890, by which time the box magazine smokeless powder rifle was introduced, and remained the most common infantry weapon until the end of World War Two. The range of this weapon also finished off the colorful uniforms - everybody quickly adopted uniforms in colors like Swamp, Dust, or Field (Olivedrab, Khaki, or Feldgrau) and being colorful became a personality characteristic, not a militarily sartorial one.
I would like to have a game were you could upgrade the guns infantry line like this:
Arquebus (16th century) -> Musket (17th century) -> Fusil (18th century) -> Rifle (19th century)
Of course this scheme is a simplification and generalization of their development, but I think could be a sweet way to represent the changes on both technology and tactics.
Personally I prefer to put WW1 on the Contempary Era than on Industrial. I mean, mechanized WW1 elements like tanks and planes are common since then, so all you need is add several upgrades on the same era, like:
Biplane Fighter -> Monoplane Fighter -> Jet Fighter -> Stealth Fighter
Considering that Humankind have changing cultures as a key element, there is not point to have many late eras, because the changes are mainly on technology and some social and economic related elements, but the development of ethnocultural entities is limited. I mean we can easily have:
1- "Early Ancient" Sumerians, Elamites and Minoans together with Egyptians and Harappans
2- "Late Ancient" about Assyrians, Myceaeans, Hittites, Nubians and Vedics.
3- "Early Classical" Achaemenids, Romans, Armenians, Carthaginians and Mauryans.
4- "Late Classical" Sasanids, Goths, Huns, Kushans and Aksumites.
5- "Early Medieval" Abbasids, Franks, Norse, Khazars and Tufans.
6- "Late Medieval" Berbers, English, Hungarians, Mongols and Cholas.
7- "Early Modern" Spanish, Dutch, Poles, Ottomans and Mughals.
8- "Late Modern" British, German, Russian, American and Omani.
The changes of the last couple of centuries could be modeled by in-era changing mechanics, instead of force over specific short lived adjetives to the name of the same cultures (please not a Japan culture for each emperor!).