Humans are fans of lions. So, so, so many groups used lions (and eagles) as their symbols. I guess something about apex predators is appealing to megalomaniacs?
Fun Fact: despite all the lions, eagles, etc, the most common heraldic animal (aside from Fantasies like dragons and griffons) is:
Bears.
Especially in the emblems of individual cities and principalities, where they appear all over Europe: Berlin and Berne (both named after bears) most prominently, bu they are, literally, Everywhere.
You forgot the most important thing. Supply lines. Alexander had fresh troops arrive to reinforce his army after any loses of lives he had suffered during his battles and sieges, even if those loses are considered minimal for the task Alexander undertook. Had Pyrrhus or Hannibal get reinforcements during their wars with Rome, Italy would have been conquered before the Ostrogoths. Hannibal lacked the necessary support from the Carthaginian fleet, and armies sent from the Alps and by sea failed to reach him. Pyrrhus despite his underrated brilliance waged war with a loaned army apart from the Epirote troops, and he never received reinforcements to replace his lost soldiers after each battle with the Romans.
Now that I'm thinking about it, a healing ability on military units fits Alexander rather well, but it needs to work more consistently than the version of Civilization VI where the healing triggered only when a city with a World Wonder was captured. Perhaps, it will work better if the healing triggers on every conquered city or would that be too powerful? We are talking about Alexander the Great though.
I never forget supply lines. My professor, Dr Borza, had every one of his graduate students working on a Travel Time project for the classical middle east for several years - gleaning every tidbit out of every account in Latin, Greek, Aramaic, et al to put together a data base of just how long it took to get anywhere from Afghanistan to Spain. They were still working on it when I left academia to get a job, and I don't know if they ever finished it.
In game, much I would love to see such a thing attached to Alexander for the sheer historicity of it, putting such a mechanism together required a considerable organization of the entire economy and strength of Macedon: recruiting people from 'home areas' for each taxeis of the phalanx and having an organization to move them from Macedon to whatever End of the Earth Alexander had taken the army to. They did it brilliantly - as well as any army in history up to the Modern Era, but it either has to be a Given for Alexander or require a considerable alteration of Macedon's normal economy and structure.
Good thing about that, though, is that a similar organization of recruitment and resources also appeared in Sweden under Gustaphus and Oxenstierna in the 17th century CE and in Prussia under Fred the Great that was one of the great strengths of those states and armies, so any mechanic need not be unique to Alexander and the Macedonians.
