In CIV 4, War elephant is a generic unit with Khmer Ballista elephant as a unique unit to replace war elephant
In CIV 5, Siam, India and Carthage has elephant as unique unit but these 3 unique units do not replace the same generic unit like Naresuan Elephant (I think it should be rename as Chang Suek which means War elephant in Thai) for Siam, Indian War elephant replace chariot Archer and Carthage African Forest Elephant replace horsemen. Thus, no war elephant as generic unit in CIV 5
In CIV 6, War elephants are unique unit, Khmer has Dombrey, India has Varu and Vietnam has Voi Chien
For CIV 7, I think there should be a generic unit for war elephant with an elephant as a resource like in CIV 4. For civs has elephant as unique unit should respawn near the area where elephant resources located or make an option like unique elephants can use horse as a secondary resource if there is no elephant resource nearby.
I think War elephant should be divided into 2 units one is for War Elephant with melee/archer and then Musket/Arquebus elephant in Reinassance era.
if there is elephant bombard/cannon as unique unit it should replace bombard and cannon. Interestingly that Siamese in Humankind also have Gatling elephant as unique unit, I believe if CIV 7 make Siam having Gatling elephant as unique unit it should replace Gatling.
Elephants have been used in a variety of ways in warfare, but there is an interesting dichotomy to all the uses: hey all reflected what each society thought was most important or fundamental in battle.
As Victor Hansen has pointed out (and made a nice academic career out of elaborating on it) the "Western Way of War" from at least the Classical Era was Offensive and In Your Face: the Greeks, Romans, Germans and Gauls all charged right up nose to nose and tried to kill you with hand weapons. In 'The East' from Mesopotamia to China, the preferred battle was to stand back and shower the enemy with missiles until he either left or was so demoralized you could walk over him.
War Elephants reflected those two different 'combat styles':
The Carthaginians, Diadochii and other 'westerners' used Elephants as Assault Weapons, possibly inventing the Howdah as an extra platform for attacks, and armed the elephant riders with javelins to break up enemy formations at close range and long spears (the Macedonian Sarissa, or pike tuned out to be perfect for this) to stab him from Above while the elephants trampled them. Of course, if enemy attacks or missiles upset the elephants, they were equally capable of stampeding back over your own troops, and there wasn't much the men on top of the elephant could do to stop him (some mahouts carried a long spike and a hammer with which to drive the spike into the top of the elephant's spine behind his head, since killing him was frequently the only way to stop the panicked pachyderm before he completely flattened your own formations)
In India and Southeast Asia, elephants were Missile Platforms. They carried men armed with bows, later firearms, and acted as elevated Firing Positions to slaughter the enemy from a distance. They took adantage of the fact that the great defect of missile fire is that before gunpowder the missile troops had to be close enough that a quick charge would send them running - or they died in place. Charging an elephant to get at the archers on top was a much less certain thing, and might very well result in stomped spearmen while the archers keep right on shooting undisturbed. (The
Humankind Mauryan Elephants reflect this: they are Ranged Troops but don't have the malus in melee that most Ranged (archer) troops have, which, by the way, makes them extremely effective Classical Age combat units) They also frequently took advantage of the greater hauling capacity of elephants to carry greater quantities of arrows than a single man could so that the archers could keep shooting much longer, or carry heavier missile weapons, like small catapults, jezzail long muskets (weighing up to 40 pounds and so not really a normal 'infantry' weapon) or the famous Siamese gatling guns (which, by the way, in the
Humankind illustration, are shown as Maxim water-cooled machine guns, which is actually more accurate historically)
So, there is a place for both 'generic' War Elephants available to anyone who can get elephant resources, which you could specify as either Assault or Ranged troops, or some very specific Emblematic/Unique Elephant units like the Mughul armored elephants, Siamese 'gatling' (machine gun) elephants, or the Khmer Catapult/Ballistae elephants for specific Civs/Factions.
