These are powerful ranged troops each carrying their own scientific wonder. The crossbow comes in many shapes and sizes, most of which can punch through medieval-tech armor without much more than a hard-tipped bolt. Crossbowmen move as Infantry and their natural special ability is bloody, brutal Wall Defense, increasing the Might of all other units in the same Army as long as they're defending.
Base Social Class
Crossbowmen, despite their usefulness and power, are recruited from the Peasants. Peasants don't get tangled up in what they think they know. When you train them, they learn how to run and shoot a crossbow and don't worry about the rest. These troops still live in Peasant Housing and require Happiness from the district in which they are housed. While living in their old housing, they can also be trained and accessed through a Garrison or recruited into your personal Army.
Base Character Class
Crossbowmen rely on sight and, to a certain extent, knowledge of the land. You don't want to stop and reload a bolt in the wrong place at the wrong time. This need for intelligence and a certain canny attitude causes these units to level like Forester heroes. This cross between commander and caster attributes makes them somewhat unique from most other non magical troops.
Crossbowmen are some of the finest Peasant troops available. They only require one material to train them, but that material is Fillets. These valuable and delicious cuts of fish will help the Crossbowmen keep their wits sharp and their bodies strong in preparation for brutal ranged battle It should be noted that 'deconstructing' a Crossbowmen unit will return Fillets. This does not mean they are made of fish.
These troops are canny, but not complicated. All they need is their crossbow and the ability to stay alive. Thus, when equipping them, you can of course give them a better crossbow than what they'd normally be carrying around Likewise to protection, these hardy Peasants can be convinced to wear a little Studded leather armor.