Battle sling for the Field Engineer
Footman class throws nothing, why not give a battle sling to the Field Engineer and 6 ammo (cast iron balls). This medium-low range weapon is in the «Tertiary» category or as an activated ability. Also two-handed weapon size as longbow and crossbow has and any Field Engineer weapons have.
Field Engineer can hold his Primary weapon in one hand use this Battle sling for a quick single shot after a certain delay. Reloading uneguip Primary his weapon or he do it with Primary weapon in hand. Damage the same as throwing knifes, but blunt attacks and a little further throws.