Reports should be sent using a PM to bounty manager. Problem solved.
Have you tried doing that? I've sent PMs to signature managers paying in BTC, and not bounties which are a little more respected for their quality wise. Yet, they didn't care. In fact they didn't even bother answering me. I linked several posts of the offenders posts that I reported at the same time. They were removed. They don't care as long as they are getting paid.
If you tried this method with all the bounty managers do you really think they will care? Especially if they are running the bounty for their company, and aren't hiring an independent bounty manager.