What if instead of just "Barbarians" we could have different cultures and factions attacking our civilisations? It doesn't have to change much of their role, but rather to aestheically seperate them into different "groups" of Barbarians and maybe generate each group into a shared area in the map. Historical nations which have been viewed as uncivilised Barbarian bother by others may be presented in the game as a Barbarian group - Goths, Huns, Xiongnu or Gauls may be some examples. I post it here but also hope to see some modders adopting this idea. If some greater coding ability comes to our aid, we can play more with this. Apart from setting a vague geographical area for each group and possibly colouring their Flags differently, we can think of other elements to add to diverge those groups. Arranging them into different "characters" of Barbarians seems to me like the first interesting thing to do. In high generalisation - Woodsmen, to include the Goths, Gauls and such; Horse Nomads, to include Huns and Xiongnu and others; I also though of Seafarers, to include Vikings and whichever else fits in that category. It may decide which units they spawn - Mounted vs Melee. Or may decide what their goals are - Pillaging improvements vs Destroying your units. It could also decide on what terrains they spawn - in Jungles and Woods or in continuous Deserts and Plains (this one may not work in most kinds of map though). The initial idea is based on Civ4, which is the edition I play the most, so sorry if some of the terms i used were archaic in a way... Anyway, imagine that you invested your whole early game in survival against the Mounted threat of the Huns. Later, when you discover another, emptier, continent, and send settlers to it, you learn the hard way that in there you have to deal with the now "exotic" Xiongnu radiers.