Since it caught your attention I would like to elaborate on that idea. Making promote work might be a big part of Steem success economically speaking. This topic might even need its own thread. Sorry for going off the topic.
First, if 50% of it is burnt it would reduce the supply of Steem which will increase the value. For this to happen both authors and curators should be incentivized in using promote feature.
Second, if the remaining %50 percent is added to curation rewards, more curators will be visiting or setting up bots to upvote promoted content.
Third, more and more authors will start using the promoted feature. Because now they know regardless how much they spend curators are incentivized to go through the promoted section. This might change vote buying behavior. Instead of buying votes authors could use promote feature.
Fourth, if more authors use the promote, more Steem is burnt, which again decreases the supply of Steem and increases value of Steem.
Fifth, this can become a great way of advertising on Steem and can attract companies to invest. Currently, there is no straight-forward advertising component of the platform that works. Obviously, traditional ways of advertising will never be accepted by the community. We need a mechanism that works to attract companies to spend their ad money. This will have to be figured out at some point.
Lastly, I want to thank you for starting this conversation. This post might be the reason Steem price is going up since yesterday. Last time this kind of Steem price rally happened when Ned announced SMTs. Market seems to like when leaders of the platform are discussing improvements on Steem.