Great points! Have you seen the posts about User Authority? I think something like this could replace the current reputation score and be a form of checks and balances on steem power.
Here are a few links about it in case you haven't heard about it yet(one is mine)
https://steemit.com/utopian-io/@scipio/how-to-solve-spam-on-steem-introducing-userauthority
https://steemit.com/utopian-io/@scipio/userauthority-ua-explanations-applications-and-implications
https://steemit.com/steem/@littlejoeward/fixing-the-reputation-score-and-eliminating-spam-a-follow-up-to-user-authority