No, I don't mean a materialization-tradition magician teaching his spirits the Possession power. I mean a magician learning to possess someone else while astrally projecting.
Possession
Prerequisite: Must be able to astrally project.
The Possession metamagic effectively grants the magician an ability equivalent to the spirit power of the same name. It follows all the same rules, with the exception that the magician's Magic attribute is substituted for Force. Rules for vessel preparation also apply. Vessels possessed by a magician rather than a spirit do not gain Immunity to Normal Weapons, or any attribute bonuses; rather, the possessing magician's Mental Attributes temporarily overwrite the vessel's (if the vessel is alive), while the vessel retains its Physical Attributes. In the case of a living vessel, the magician also cannot access any of the vessel's skills, nor use any cyberware that requires activation. Possession by a magician may not be immediately obvious to mundane onlookers, but an Assensing + Intuition [1] test will immediately reveal that a person has been possessed. Note that if a person suddenly displays a drastic change in behavior, those nearby may become suspicious. In any event, the possession may not be sustained beyond the limit of the magician's ability to project; the magician must depart the vessel and return to his or her own body within (Magic) hours, or his or her astral form will die.
Basically, I see this as an aid to infiltration and reconnaissance rather than a way to dominate in combat. What do you think?