You realize Oda already revealed the cultural background for the characters, and Zoro "is Japanese," which I take to mean he would be Japanese in the real world.
Actually I didn't! It seems that this was quite new SBS-info so I hadn't read it yet, thankx for the info..:) But know we know it for sure, briefly.
But I still don't think that Oda wants to make any any crew member a perfect model example of the country that the character origins, and after all that list told us what countries they would come from(=what basic cultural traits/customs/looks they represent), not what exact ethnic/cultural background they might have.
But I must say that it warms my heart to hear that Nami would come from Sweden, altough I can't see anything especially swedish about her