I don't know where to begin on this other than to say handling a full-auto handgun is far worse for untrained personnel than a semi-auto handgun. It's even a challenge for highly-trained personnel.

Additionally, the very long history of machine pistols would indicate the form-factor is a poor fit for the application of any full-auto fire.

This is the primary reason that personal defense weapons (PDWs) were developed in the first place.