I think the five class system works well. However i am not a fan of Army. A medieval army was comprised of Nobles, soldiers and peasants. Dependent on the time in history the ratio of nobles, soldiers and peasants which formed an army changes. This ratio also changed dependent on country and if it was an offensive campaign in a distant land or a defensive campaign within ones own country.
what was a soldier in the middle ages....one that got paid! Generally household troops, Mercenaries and Freemen who were generally more skilled then levied peasants. Levied peasants were only obligated