That's great if you want to do it, but in my experience doing that sort of thing for another site some years ago, running cleanup on this shit is just a band-aid, not a real solution (which needs to involve preventing them from posting in the first place somehow).
Anecdotally my impressions from that experience have been that the ones responsible are 1) Not bots, but keyboard monkeys, so that anti-bot measures like captcha don't really help much. 2) Probably mostly originating from or running their servers in Russia and/or China i.e. places that tend not to be interested in responding to complaints filed from abroad. (I remember one outright posting after some deletions trying to argue that "child nude models" weren't illegal in Russia and so there should be nothing wrong with the deleted posts) 3) Leaning more into conspiracy territory but I'm not entirely convinced their purpose is actually just spreading CP and not some other scam or nefarious purpose, but I'll leave further speculation on that as an exercise to the admin. 4) The admin of the site in question refused to take my suggestion to implement an anti-TOR filter so I can't tell you if it would have helped or not. I still consider it a good idea, "bluh bluh muh legitimate uses" arguments notwithstanding, but nowadays I'm not sure that TOR is the IP-hider of choice anyways.
Again, this is anecdotal speculation but if it helps you come up with anything, do with it what you will.