for now maybe a public voting page to propose blacklists then a moderator team from the 3top bot can say yes no if yes it goes a weeks voting by lets say at least 200 users or all witnesses the list gets updated and all bots need to check that api before accepting bids. ... not sure if i would trust general users to vote though.
Thinking is just a simple api that will return a clean json reply with usernames and from there it can be expanded. Your bot can already merge markymarks list also, and with time it will be the norm.
Sorry to load the reply. But also implementing a value cap of how much something may worth, there surely is a limit to how much any post could possibly worth since the people are paying themselves, and assuming they are actually losing money on bids it still messes up visibility for legit posts. That is all sorry for the mess.