To be honest, the way stun guns work seems pretty OP and also somewhat non-sensical to me.
The fact that MPs are WIT + EMP means, that e.g. soldiers or strong creatures are much more affected than weak but smart and emphatic characters. It doesn't help that stress ignores armour...
As an example, my group encountered a Nekatra. What could have been a tough fight was cut very short by my PCs by using a stun gun. Nekatra have 11 HP but only 4 MP. Two hits and the beast was down.
Stun weapons are described to affect their target through electrical pulses. Why should an electrical pulse affect someones mental state? What's more MP recovery works differently than HP recovery. Why would someone who was hit by a taser get PTSD or something (at least it should be more likely than when someone is attacked with lethal weapons, right?)?
Any suggestions how to deal with this?