Simulate one human life, from beginning to end, in a way that allows unethical experiments to be dismissed as recurring nightmares by the individual, and not cause permanent damage to this simulated person. When their life ends, I'd arrange to talk to them, explain everything, apologize for the necessity of the experiments, and offer him immortality and/or freedom with no strings attached. He can get a biological or robot body, or stay virtual, but it's not up to anyone but him/her/? at that point.

I'd be fine with my life being an experiment under those circumstances as long as the results were put mostly to saving or improving lives, but I'd never be willing to put someone else in that position if I didn't; if you couldn't find a person like myself in real life with that opinion on the possibility, it's unjustifiable. If, however, you engineered their life just enough to strongly encourage that level of altruism, and made it comfortable and not dehumanizing when not involved in an experiment as well as having a ban on cruelty and gaslighting in doing the experiments, and apologize for having to resort to these measures at all, I could see the person not being overly upset.

Whether it meets the code of ethics for scientific research is another matter.