Sure, and you could say the same thing about unit 731. The argument is not that it is inconceivable that there are benefits, but that they should be weighed against the drawbacks, which you don't mention at all.
I want to be clear: I hate this. I hate everything about it. HOWEVER...
If you want to argue against wetware then we need a better argument than this. The same ideas were used to argue against stem cell research, IVF, and many other treatments and ideas that have saved and helped lives. Unit 731 isn't an apt comparison because cells are not inherently sentient to our knowledge. If they were it would absolutely shatter the profession of medical ethics as we know it.
How is unit 731 an apt comparison here?
Those were unethical experiments from the onset.
If anything, my argument would be more "just because unit 731 ended up doing live vivisections of humans, that doesn't mean we should have outlawed dissection of dead humans centuries earlier".
I don't think it's a good idea at all to try to outlaw totally reasonable research just because we can imagine a future where people end up doing a much more extreme much more problematic similar thing.
It would be the end of science. (and the end of any culture really... we're very good at imagining future dystopias and armageddons)