Yes, but in some cases it's about realism in the very practical sense of the word. No matter how you look at it, the lack of any sort of armor in medieval times (I'm talking about the Greek units now) for the core units of an army just isn't right. [...] Also, the use of heavy armor after gunpowder is also strange (Roman praetorian Grenadier - I have not seen this unit, but I can imagine how it looks).
I agree, which is why I said they might be more realistic, but they won't be historically accurate either.
If there were plenty of additional units to choose from, I would also replace some of the ones I currently use, but I rather have a roman grenadier with armor (for which I completely agree that it is too much armor) than to have 40 grenadiers all looking the same except for the color of their uniform.
Some variation is imo desirable here, it shouldn't get too unrealistic however (which it currently, out of necessity, sometimes does).