We already know that nations divided into categories such as agrarians, expansionists, etc. 

But some nations are not only mechants or scientist, are they? So, the question is, will we see any mixed fractions like builders/expansionists and else? Or the game designed for us ourselvs to create such a nation?

With Babylon, which is the only culture whose EQ, EU, and legacy bonus have been revealed, their primary bonuses are scientific, but by giving the astronomy house bonus science from being near farms and granting extra food from researchers, there is also a sort of secondary bonus towards agriculture. I'd guess they could do that with other factions as well, where there is a sort of synergy of different aspects of their culture, like Arabia being scientific and religious or Britain being builders and expansionists.