Is it possible to commit a "copyright suicide", for example to show disagreement with the system, by publishing a waiver (such as CC0, digitally signed to confirm it was really me who published it) stating that it applies to all past and future works one creates?
You can certainly release any or all of your existing copyrights under a CC0 or similar license which allows anyone to treat them as essentially public domain works. You could publish a statement of intent to do the same with future works. But I don't think that such a statement would be binding on your future actions, nor that another person could rely on it with assurance as regards works not yet created as of the time of the statement. I think you would need to release each work in turn as you create it to have this effect.