This really should be it. Open up but slowly deteriorate the experience.

Here's a concrete proposal: Set automod to delete any post/comment longer than 20 characters.

This makes discussion virtually impossible, and starts to impact the quality of Reddit posts. With enough subs cooperating (e.g. the subs that went private over the blackout), it'd already be making a serious impact on the usage experience of Reddit. Furthermore, this policy can be enacted indefinitely without stopping the "regular operation" of Reddit (i.e. mods can sit on this policy for as long as they need to, as opposed to the blackout which even from the start was planned with a time limit.)