But this implication is unacceptable. Therefore, so is the AC solution. Therefore, AC cannot entail that innocent people should be punished. The implication remains just as unacceptable. In particular, it overlooks the costs involved in maintaining such secrecy and the risk that is run that the secret might get out, causing great damage to trust in legal institutions and other significant long-term costs.
Punishment involves an institituion on which being guilty is the reason for punishing.
Once the system allows innocents to be deliberately treated in the same way, it is no longer punishment. Responses to this objection and replies to responses are likely also to proceed along similar lines. We would never treat innocent people in these ways just to promote the public good. And so we should not treat guilty people this way either. It is one thing to use an innocent person merely as a means, and quite another to treat a guilty person as such.