I've thought that it'd be interesting to publish an adblocker subscription for signatures. You can block individual users' signatures with eg. bitcointalk.org##.sig186520, and/or you can try to block signature ads generally with filters like bitcointalk.org##.signature table.
Userscripts are a good idea. Let me know if some small change on my end will help your userscript a lot.
Does it affect on forums signature(which comes from your auctions?)?
Singature adblocker is really bad idea for the campaigns. If every forum member will start using this then there will be low result for signature campaigns.
And it will prevent upcoming campaigns.
and yeah there will be development(ad blocker for signature, not for specific users, for every users) in this ad blocker will come and it will attract users to use this ad blocker and this will affect on campaigns(likely not on running but upcoming campaigns).