I don't think it's possible to stun the Chrysalid or any of the robotic enemies. The only thing that i see is the upgrade that allow you to mind control the drones, which seem useful if they're able to heal your S.H.I.V the same way they do the UFOs. Stunning the Berserker was surprisingly much easier than i thought, since you can just lure them to your squaddie equipped with AT because they chase anyone who shoot them.