I proposed something very similar if not identical in response to an early proposal by Dan in how to revamp the curation rewards. (Neither Dan's proposal nor mine was adopted).

Both your suggestion and mine are based on the fallacy that the eventual payout is a "fair value" that can be predicted. This is not the case due to the circularity, especially in the case of whale votes (since it is the votes that determine the eventual payout). There were some other issues with it but that is the key conceptual error that undermines the viability of it entirely.

Also, some sort of superlinear payoff is needed otherwise the incentives favor voting for your own posts regardless of popularity or merit, either directly or via shill voting.

In thinking about this quite a bit over the past few months I've also come to believe that superlinear payoff is economically correct for a platform like Steemit, because only posts that are of interest to a large number of people benefit from being shared in this manner. If something is only of interest to a few people (dinner plans for example), it is better to share it privately via email (or private Steemit messages once that is implemented!) and not impose both the resource and clutter costs of sharing it with thousands or millions. So something of interest to 100 or 1000 is worth more than 10x or 100x something of interest to only 10; the latter probably has close to zero or possibly negative value (once costs are considered) on Steemit.

All of this is not to rule out that tweaks to the current model might be helpful, but getting all the incentives right after considering all the relevant factors is much harder (and I would suggest the current system is much better than many of its detractors claim) than just wanting to make them "more fair". It is also not always so easy to see the various perspectives on how the current system performs multiple useful (and even essential) functions, when focusing in narrowly on one aspect of it such as perceived fairness.

I do like the idea of providing some sort of incentive for valued downvotes; perhaps some version of these ideas could be applied in a more limited manner to do that. But even there, getting all the incentives right and avoiding opening up vectors for abuse is not easy.