Thanks for the comment Kevin. Hopefully a few useful clarifications!

Other than maybe (just guessing) computational complexity of the distribution mechanism

Taking a simplified example of how I think it would work, if my vote is worth 100m rshares, then if I set my curation slider to 50%, I get (the vests value of) 50m rshares and the author gets 50m rshares. If I set my curation slider to 0%, the author receives the full value of the 100m rshares and I get no curation. There is no interaction between the votes of different voters on a post, so the calculations should be much simpler than they are now. This should decrease computational overheads for the blockchain.

In short there'll be a secondary market at 50/50, or even the voting slider.

I think that if the voter sets the curation slider then there should be no need for a secondary market, since all voters can extract the desired value of their vote from the "primary market" and cannot achieve more in a secondary market than through the primary. Users who currently delegate to bid-bots could instead set their curation slider to their desired fixed percentage and trail "Trusted Curators" for the community / tags that interest them. This would direct visibility (and most likely some reward value) to the best content.

Plus wouldn't a slider just cause most voters to go for anything 100% curation?

Perhaps. Although currently any user who wants 100% of the value of their vote can simply sell their delegation / vote on an alt / join a circle-vote etc. Pretty much all of these damage Steem, particularly bid-bots, as the end result is the promotion of poor quality content on trending. I expect (hope?) that the users who currently do not follow these approaches would retain a level of author reward distribution, perhaps 50/50, perhaps the current 75/25, but decided at their own discretion. And flexible.

Then hopefully bringing the passive investors (bid-bot delegators) back into manual curation or a "Trusted Curator" system would also bring back some author rewards (even if only the margins that currently go to bid-bots and vote buyers).

In the end I think that people are ingenious and will always circumvent whatever constraints are implemented to extract the full value of their votes if they really want to. The proposal tries to work with that, allowing all people to participate in good Steem behaviour (i.e. voting on the best content) whilst allowing each user to take a level of rewards they deem acceptable. And at the same time allowing complete flexibility so that different Steem users, dApps and businesses can distribute their rewards in line with their own specific needs.