Gladiator (Black Hat) Chinese are Ch'in and work for Han or 3 Kingdoms. Definitely not Shang or Chou.
Essex is the best solution at this time.
With respect Goragrad the Chin figures could be more apt for a late Chou(Zhou) army as the state existed as late as 256 BC which overlaps several of the Warring states.By the cut-off/start date (480BC) between the Autumn and Spring period and Waring states the troops could probably look more closely to the terraccotta army.
A valid point Haardrada, but then you lose some of the visual distinction between armies.
On the other hand, the trousers were adopted based on contact with the Steppe nomads and Qin is on that border while Wu and other kingdoms were interior or on the coast. Chinese cultures historically tended to be conservative and I would not be surprised to see the other states retain clothing styles for some time after they were first adopted by the states with direct contact with the nomads.
Armor and weaponry on the other hand would probably be more rapidly updated.