You won't and quite literally cannot win this.

As long as there is any financial incentive for bots then there will be bots and people who build them. If you reduce the incentive for humans to post then you actually increase the incentive for bot posting because people won't feel as inclined to make thoughtful and insightful commentary. This is especially true so long as any single whale can drowned out the voices of thousands of users.

The new rules going into effect at the next fork make human posting a dangerous game. You're limited to 4 top level posts a day and one every 6 six hours or you pay a penalty on your earnings for the day. This is true whether you are a bot or a human.

Something needs to be run on a timer to maximize revenue? Check!
Redundant task, that literally no one cares about because if they did the rewards wouldn't so heavily favor automation? Check!

People will flock to bots simply because posting more than 4x daily carries a financial penalty.

Totally wrong minded approach. A better approach would be a tool that gives the minnows some strength to flag spam because you don't really hate the bots, you hate the spam and that's a totally different ballgame.

Posting spam of any kind whether by human or bot should remove your post from the site and cancel all your earnings and posts for 24hrs. That will stop bots. Nothing else will.

The reason is that the spam bots are just griefing you. The fact that they make money is just a bonus. Some people just want to watch the world burn. But they are no different than any other trolls, just much more effective at spreading the message.

Incidentally, I've been discussing building tools that hybridize human & bot to allow the minnows a lot more power than we would otherwise have. It's still a bot, but it's driven directly by your preferences and desires.
https://steemit.com/steemit/@williambanks/bot-warz-a-hybrid-approach
Feel free to go there and comment about it, I'd be very interested in hearing your thoughts.