You guys should check out the Realism Mod at TWcenter.
It tweaks and balances a lot of the factions, units( and removes the silly ones), and names. Egypt gets a big working over being completely changed to the Ptolemaic Empire, gaining more modern Egytian units, losing ancient ones, etc.
It also has numerous changes to the AI and includes the killspeed/run speed mods, I posted a link in the modding thread here.
On the discussion of balance here. I think single player is a poor way to judge the balance of a unit. For example, I had problems with Scythian chosen warband archers in single player. Is the unit "warband archer" overpowered? Probably not. It could have been the Scythian temple bonus that was overpowered, and nerfing the unit may nerf it for other races.
The best way to judge is multiplayer, if you're finding one unit there (where all things are equal) owning the battlefield in a combined arms situation (and not against its matchup) then yes it needs to be looked at. There is also the issue of histroical accuracy too, but Im no expert on that.
There is also the other side of the fence, a lot of people get their ass handed to them by a unit and cry out "unbalanced" because they simply dont know how to handle a particular unit, or let their opponent exercise the units strengths.
Units such as chariot archers do have a weakness, that is melee. But if you cant catch them you can never exploit their weakness, so really they dont. Playing against the AI you can trick it into being trapped in a melee (exploiting the skirmish feature), again, this is why singleplayer is a poor judge of balance. But multiplayer a human is not so stupid.
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