I don't agree that earnings by bid bot delegations or selling votes are in any way tied to behavior. The risk is moved to the customer
This is true. But at the same time, the only real risk right now is that the customer doesn't achieve a positive ROI. I don't have a problem with heavily botted posts on trending getting knocked down a few pegs and losing money, as that at least better falls within the model of bid bots as advertising services. No one should expect to be paid to place their content on trending.
I've always hoped for a revamp of the inbuilt promoted post feature (breaking it out of the segregated promoted tab and into trending content and tag pages) to arise and undermine some of the customer base of the bots. At least then the funds are plainly spent on advertising, are burned to the benefit of Steem price for the whole community and eliminate the bot operating middlemen, and the rewarding votes a post receives from the higher visibility are actually organic.
That doesn't really happen though, and I don't see free flags as a solution. They'd introduce other negative side effects, and his bots would probably just get a little cheaper. We don't have any need for paid promotion besides the inbuilt one (which definitely needs a better presentation).
I think the issue of flags and downvotes could be a very simple solution. A two tier flag system. If a post is flagged for any reason other than rewards, then the author of the post gets the flag. If the post is flagged for excessive rewards, the the person or the bot with the largest reward issued gets their entire amount flagged erased, 0 reward all returned to the reward pool. The other voters that were generic still recieve a little bit from the left over rewards for their curation efforts. If a second person still thinks the reward is to high then the next reward gets removed and so on and so on. It will not take long before bid bots start themselves a list of bad players. It will not take long before rancho type people find another method. If you want fund the new investor pool with rewards that were rejected by the community. Plagiarism and copy paste and spam content will still get flagged and the author still have his reputation decreased, but they would no longer be able to lay the blame of their demise at the feet of an over zealous reward flagger, their rep hit would be well deserved, right now not all people with reps less than 0 are schemers and scammers.