@iamtakingiteasy @lina @menherahair

If they aren't using a media proxy and you have access to eientei, wouldn't it be possible to capture their IPs with dms using a unique small custom image for each one?
Just have a script generate the images and create the dms, save image-target information in a spreadsheet, fire it up, and finally check eientei logs for hits on those images in order to cross correlate with the spreadsheet.
Could scare them enough to defederate you from the beginning but then again could result in them hardening their instances with a media proxy.

Perhaps execute the above process for a couple of months without announcing anything, and make sure that the DMs and images appear to be independent, until you have a couple of hundred/thousands IPs to release in order to maximize the effect.