I like to add something to what you've said: mostly, since Alexander was able to win battles using the battle model created by his father (and turned almost to perfection by himself) to what seemed all the different armies of the known world, the Diadochi didn't want to simply abandon what seemed to be the "winning formula". But when confronted with each other, it was hard to win against an army that was so similar to one's own, that they decided to add small exotic elements in the hope to gain a decisive advantage, such as Elephants, chariots, and other mercenaries/soldiers. Usually the backbone was composed of hardly replaceable Macedonians, coupled with native auxiliaries or mercenaries. Maybe the first could be given longer recruitment times, whereas auxiliaries and mercenaries could be easier to recruit (but more expensive and a smaller recruitment pool in general, to avoid AI spamming). That would be my suggestion.
I don't think it would be fair to generalize all the generals of a faction (in that case, Romans should have a terrible LoS, Carthaginians should have command penalties for attacking, among other "chiches"), but maybe it could be a good idea that those generals with a "hellenic" ethnicity trait could get a higher chance of developing negative command traits.
I won't say much on the recruitable generals there... I mostly don't think much on them, nor do I know how to make their difference with royal family members evident.