I like the idea of a bustling metropolis, especially if it will indeed be LA, because like I've said previously, I'd like to see this nation in LA and providing contrast to the rest of the age (which is abundant with death/dying/decaying/corrupted nations).
I'm not sure if I like a middle-eastern theme too much. Mostly because I'm not really sure how to capture that theme, and partly because I'm middle-eastern myself, but when people talk about a middle-eastern theme they do not mean one that is relevant to me
My current idea is that we go with the "guilds" theme, maybe our city was just your normal bustling city with four competing (elemental) guilds*, and now with the spreading death, the king has forced the guilds into active military duty to help the city/nation defeat the spreading death of LA.
*-Possibly artisan guilds, perhaps ones that have separated themselves from others for a long enough time to develop their own sorts of "cults"