I'm thinking of something like the following:
Instead of randomly intruding into random people's threads, a topic starter could "opt in" to enhanced spam scrubbing by placing a special bbcode inside the OP, that (among other things) contains a "percentage spaminess threshold" that applies to all replies.
Then, I have J.A.R.V.I.S monitor the thread and score each person's reply, and the ones that fall short of the spamming score, I report these replies, or maybe I relay the posts to your bot if you can offer a faster way to delete those posts.
This is already something else than the OP's original idea (at least as I perceived it). This was a bot that would make self-moderating threads easier. Where the OP of these threads could request to use this bot to moderate the thread. A bot to help with that can be useful for doing ANN or something like that.