well, i put a goblin cage just near a pit, and assigned the gobling into the pit (15 stories pit ^^). The peaseant that freed the goblin got a nice red troath, 2 eyes looped off and it falled incoscient into the pit. the next peaseant just pick up the goblin (undamaged, and hostile), and threw into the pit...
now i have engraving like "a goblin falling", " a dwarf falling"...
you dont lose a gear each time you open a cage... the mechanism attached to the cage is just near the cage, and the one attached to the lever keeps in the lever... so you end with a lever full of gears and no use.
and for the parties... kill the child or deconstruct the statues... or the 2 ^^