The promotions tab is supposed to help, but few use it, unfortunately. You burn SBD to promote a post which, in theory decreases supply of SBD which should increase value of existing SBD. I'm still hoping <a href='https://steemit.com/steem/@dan/steemit-s-evil-plan-for-cryptocurrency-world-domination">this plan for world domination will still happen at some point in the future. That was one thing I was the most excited about when I first joined Steemit. I was sad to see Dan leave the team because of this vision, and I don't want it to die.

But yes, I think posts from the promotion tab sprinkled within existing feed content would be a nice way to go. It could even start as a setting people could opt out of if they didn't want it (but default it on to begin with). My hunch is, the promotion content would become more important overnight if that happened.