I like this idea. I was already thinking about ad spending being distributed to the daily rewards pool (including SP interest)  rather than burned to null, and the opt in/opt would be great. I don't know if it would be technologically possible to implement those calculations. 
The promoted page makes no sense. I also favor ads as promoted posts (not standalone graphics/text like Adsense), that are given prominent category exposure based on an ad rotation, percentage of impressions = percentage of ad spend type system.

On first impression, one would think that this is already what steem does... but posts fly off the front page in seconds unless they're interacted with, so I'm sure an algorithm could be come up with to estimate the value of the time that a post spends on the front page. It would be even cooler if you could target your audience, or if you could see stats about time of day and viewership, even cooler if you could see that based on audience interest... lol!