If we do a Spirit Rescue for someone as insurance so the person could not be trapped in the astral, the incentive to attack the human to trap him/her there would be lost. That being the case, could a Spirit Rescue “in the bank” ever be a deterrent to extraterrestrial attacks?

It will not be a deterrent because the interlopers will not be aware the insurance policy is present. So it will only be the case that as a person reaches their moment of transition, and the divine realm goes into action to help them, any spirits present anticipating this or being called in as reinforcements to engage with the departing soul to begin the transition will be met by light emissaries and their plans will be thwarted. So it will not matter if they are anticipating a fight or are unaware, they will meet with opposition at that point in time. The light will win the day and you can be sure the Protocol will be carried out effectively. The only caveat being the readiness of the departing soul extension to cooperate with the light callers. If that fails to happen adequately, protections will be left to keep things, in terms of harm, to a minimum until a further round of healing and outreach can be brought to bear, so much will be gained.