Okay, according to various history books and articles, camels were used in the Achaemenid army as mounts for troops sometime after 420BC. Before that, and thus in the mod's timeframe, they were used as pack animals, to carry supplies and such. Herodotus mentions that in the siege of Sardis camels were used, but only to frighten the enemy's horses with their smell. So, the Persians did use camels, but not in combat, at least not in the Greco-Persian Wars.
Now, what I've read about chariots: They were used, but only by nobles, and not all of them, because they were considered obsolete by then and more like a status symbol than anything else. They were impractical in combat and especially useless against a heavy armored oponent -like the hoplite- fighting in formations and not unorganised.
As I mentioned in the comments section, I have in my hands a couple of camel models from OSP packs and I have made a couple of chariots, that, while functioning(meaning they can be used and be ridden by player and troops) they lack the proper animation. It is a rather minor thing, but if someone looks at them in the battle, he will notice that the chariots have a more gliding motion than a galloping one. That's the only thing, other than that, they are completely functional.
So, I would like to hear your thoughts and of course, your info, in those two issues. Should I add camels and chariots? From a more historical point of view, they would not be that historical. But I would be happy to hear what you have to say on the matter.