Okay - the issue on my mind has to do with origins. We have two major ways in which azmothian humanity is fractured: element and nationality/race.
I guess my first question has to do with nationality/race. I was assuming that each nation you created is populated by its own race, for the most part. Like France is home to the french, Bask is home to "Baskers." (I just made baskers up, and I kinda like it.) Is this assumption correct?
My second question is, did the races/nations develop in the south, post-exodus, or were they existing in the north prior to the order to move south?
If they developed in the south, it would be a stretch to have a tarthite forest human, or a tylerian desert human. If they developed in the north, what elements are common to that race depends on what their lands were like in the north.
Here's a possibility that might make these arguments moot. You mention in the above postings an undefined, yet very real, biological interaction between humans and the environment (i.e. a stormy sea makes for a temperamental ocean type.) You could go further and say that prolonger time away from one's element can change type. I'm not saying that if a hill type moves to the forest and stays there long enough, he'll become a forest type. I'm saying that if hill people moved to the forest and stayed there, for generations, their ability to pass on their hill type to their children might be mutated by their forest environment, and so in time (generations of time,) hill types might begin to have forest children, in a forest environment. This capacity to adapt might be widespread, or found in only a select number of humans, or anywhere in between.
This would allow the humans to gradually adapt to whatever their environment is, and would allow for humans of all nationalities to be all types. Maybe in the distant past in the north, some tarthites were forest types. So in the south, you can find forest tarthites (though they may be rare, or not, or whatever depending on the degree of mutation,) but you can also find desert ones. This is just a thought.
That could also make things needlessly complicated. I still need to think about this; I'm not sure it makes any sense at all, really.