I think the minimum number of civs should be raised to the default. The reason for this is because having fewer than the default makes the AI much more pacifist and renders it effectively a no-war game. The AI aims for however many cities it can cope with while keeping its economy ticking over, and if there are too few opponents then every AI has easily enough space to expand peacefully (as long as they're not boxed up) so war is taken out. This would make a much bigger (and a better) difference than forcing barbarians on.