Naga Huntsmen

Living in the hills of Assam and Arakan are the Nagas, a tribal community of hunters and farmers. For centuries, the Nagas have very much stood in the way of many kingdoms and empires, fiercely defending their way of life with their proficiency in crossbows. 
For this reason, they are highly useful as mercenaries to India and the Bamar, since their may specialty is in killing the unique units of all Asian factions. It doesn't matter whether the unit in question is a Beiyang Rifle Regiment or an Bugis Warrior - all of them will fall if facing a volley of bolts from a Naga crossbow. 
for this reason, Naga Huntsmen are highly proficient mercenaries for India and the Bamar, especially if facing against an enemy with unique infantry units, particularly Siam, the Malays and the Koreans. In a large group, these units can even be used to resist the formidable Chinese cavalry, thus being ideal mercenary units in the early game. In the long run, however, they are little more than speed bumps as various factions upgrade their armies to conventional Rifled Guns and Rifle Infantry -- although it is worth noting that China must still rely on unique units in the late game.