Re: Rather than a defence...
I understand the need for a 'public interest' defence but would be irate if someone tried using it to justify hacking my systems.
Your idea has some flaws but is also in its current form very much worth submitting to the 'call for action' so if you haven't already done so, do consider raising it with them.
One challenge is the targeted party doesn't know that they're being attacked for benign purposes; they could launch countermeasures and we end up with the plot of Neuromancer.