Make a 3 piece rig... one for the legs, and one for the arms and head and one for the collision sprite.
spawn collision sprite.
spawn legs sprite +pin to collision sprite
spawn arms and head sprite +pin to collision sprite.
Use the collision sprite for your AI's movement routine. (give it the pathfinding behaviour if you re using pathfinding)
use the arms and head sprite as a turret. (give it a turret behaviour if you want to make it easy.
The legs are there just for the visuals.
not going to be perfect, but this will get you going. I would make my own turret routine, but the pathfinding AI seems to work really nice, so I would keep that.