'Castes' could simply rely on a queen/worker/soldier/drone model, though whether that transposes itself well onto the game (or doesn't leave a lot of room for creative license), I can't say. A hive mind helps protect against tantruming, but the death of the queen could cause a severe malus: e.g. a mood hit for the entire fort/hive (she's everyone's mom!)
Wasps have six legs, and assuming these would be humanoid-ish (they can stand up on two), that would allow them the use of four limbs to wield shields/weapons, like antmen. If soldiers are 1.5 human-size that would give them an adult size of about 105k, which would easily allow all of them to use several two-handed weapons, plus shield(s). That would need to be balanced out a bit, I think: maybe they have difficulty gaining experience with combat, maybe they receive poor toughness modifiers, etc.