First of all: I love this mod. Like Bandenare above, I played nearly the whole night (who needs to sleep anyway? Playing your mod is much better!). If I wouldn't love this mod, I wouldn't even care and not mention the following, so please take it as constructive criticism:
I think that barbarian mercenaries function is not good for the game at all. Their Star-Trek teleoprting ability directly into your empire is just weird.
It's, in Civ 4 as well as in reality, legitimate and logic to move troops to the frontiers of your empire, especially if you are at war. Romans did this in reality, even in republican time, before the limes was built, most legions where outside of Italia; and when Alexander invaded Persia, the first big battles (Granikos, Issos) where fought geographically closer to Pella than to Persepolis. Empires try to protect their borders, and invaders have to fight their way through the defenders if they want to see the enemies core land. But in this mod, if you put your armies together to face invading troops, some mercenaries magically teleport to your capital and conquer it.
Empires in the antiquity faced barbarians or other enemies that appeared surprisingly at their borders: Sea Peoples vs. Egypt, Cimbri and Teutones vs. Rome and so on. But when did ever appear an enemy army from nowhere in the core land of a big empire? Not even Hannibal managed this, after outmaneuvering the Romans in the Alps he had to fight in northern Italy, still far away from Rome.
I could accept quirky game mechanics in a histric mod, if they reflect something that was real or I could accept things that never happened in reality, if they are good for flair of the game. But the teleporting barbarians are neither. That magical teleportation did not happen in reality is obvious; and it's not good for the game that it's necessary to have a full army in every city because a full stack could just appear magically in front of it.
tl;dr: No Teleportation!