In our real world the history is built on one single thing - genetics of the nations, and more preсisely on the phisiological intelligence of the people. The europeans colonised the whole world exactly because of their phisological ability to resolve the complex tasks. How can small Japan or Britain or even Netherlands, Belgium, Portugal colonise much bigger nations? Why do this countries have now the best economic, science, military, etc... So if the game developers will not use this factor (phisiological intelligence of different nations) the strategy-games will always be unrealistic. I'm not talking about adding to the game the intelligent rate like techology or science. I mean that it should be determinated that for example germans will be always more intelligent throuh the game. Constantly.
P.S. We all have different heigth, wheight, color, different voices - why is it wrong to have different brains? By the way, as well as the brain is much more sophisticated and detalised device then the leg-bone, it has the potential to variete not just in 40% but in 4000% between people.