You're kidding right? barbarians are like a free pot of gold or an extra hunk of HP for your troop. I kind of like the idea of barbarians becoming minor civs. But I also think that at least the Nomadic ones should be alot stronger. Apparently in history the turks could beat just about anyone and different countries began hiring them as mercenaries. I like the idea of buying big strong barbarian troops to do the dirty work for you.
), but foreign threats of this nature at least can pretended to be solved that way. However for civ the effects should be of significant terrorists/street gangs.