I replied to your comment elsewhere.
The Vessel has the power to withdraw themselves from the ritual.
If you withdraw yourself from the ritual it ends.
The Outsiders drawn by this ritual have no interest in the physical world, their only interest is in learning more about you. Where would they run off too? If they will the Vessel to leave the circle than the ritual is broken and the Outsider returns to their home.
I do not understand how you got the idea that you "give over some else's body" the Binder and the Vessels are collaborators in this ritual. If you are forcing someone to do the ritual with you, than you are the danger and you are undeserving of power.