The way I saw the process working is the victim’s mind is downloaded into a virtual waiting room, while the Assassinis uploaded. The once the mission is complete the process is reversed. In this story there is a problem, meaning the protagonist has memories of the Assassin’s previous missions, but also importantly, he now has his training, so he can now use a fire arm and defend himself, however I do picture a scene where his body simply can’t do what he thinks he can as muscle memory is completely different thing. (So perhaps overwritten was not the right word)

Also, this would put the antagonist’s plans under threat two fold. Firstly, their Assassin is now missing memories, has memories that don’t belong to him, which makes him a more unstable killer. Secondly, the protagonist is now walking around with secrets of various missions in his head making him a target.

Meanwhile, the protagonist is not only struggling to remain alive while on the run, but now he is having to cope with almost an infection of the consciousness.

However, altering the story to so he is constantly torn between who he is and this other consciousness, which he needs access to have any chance of fighting off the constant attacks sounds fascinating. Plus could give the antagonist a chance to attack my protagonist’s main flaw.

Guess, will get brainstorming version 4.0