Also, you speak of different command structures. Do you think each faction might have its' own representative format? (I'm all in for making Warband's peoples more culturally resonant.)
Kingdoms, factions, principalities, or anything with a military tradition, no matter how big or small it is, has their own command structures in the army. You might find two kingdoms or social group of several kingdoms have very similar types of command with their neighbors, but each did something differently, mostly in the belief that it would give them an advantage, or you would get to a situation like the Crusades, the hundred years war, the invasion of the huns, or the mongols, or generally any mass migratory action that has intentions of taking things away through military force.