1. Maybe you could have it so the only person who can harvest the kidney is the person who restrained them, and once they got their kidney stolen they were immediately unrestrained, or maybe after a minute, they got unrestrained.
2. Once unrestrained they could then run to a medic or hospital. If they ran to medic it could cost them and maybe be like a windows key thing for the medic, and if they did it in the field, maybe there health would be maxed at a certain number until they then went to a hospital for a full heal. Obviously a medic can't do something in the field that a doctor can only do in an operating room. So the field heal stabilizes them or could give them longer to get to the hospital, but it would cost money in the field. Although obviously if you go to the hospital the. It would be free and instantly heal you.