I was thinking if we have every nation having very different ecosystems climatically that each nation would haves soldiers deadly in their nations environments. Like a Forested nations would make use of Thieves and fighters and generally weapons with shorter range to make up for the forest tightness. While Plains would make use of Mounted units and bow users for all that open space they have. The Cold areas if they mountains would make good use of flyers and archers and a desert would work best with the mages and flyers since in Fire emblem only mages and Clerics could move easily on sandy levels amongst the grounded units.