Make a geographically-limited pre-war (such as World cup qualifying round) where you have groups: Western Europeans, Eastern Europeans, Mediterranean Civs, MiddleEastern, African, East Asian, South Asian (incl. Polynesia), Native American, Post-colonial American. Set the rules so there's at least one civ passing for each group (two if there are many civs in that group), then have the "finals" among these civs.