Hm, with soldiers it works, but with aliens not. Neither with meleeWeapon (I thought it would work since this seems to be the method for Lobstermen), nor with adding specialWeapon through armor. Has anyone added unarmed attacks to aliens?
On second thought, do I even need to try to add them that ability? Is it supported by AI? I mean, some terrorist species attack you in melee, but sentient species do not seem to attack in melee even when they do have this ability, via Gun Melee mod. I tried unloading their weapons and throwing away the clips under mind control, and while they are mind controlled, I can make them attack in melee with unloaded guns, but when the control is returned to the AI, they are just hanging around without trying to hit the soldiers, even if they are on adjacent tiles.