I think this is very good idea and something that can bring a lot more sustainability to the system. It will surely bring the quality of the posts around the platform to a higher level as it is going to be more difficult to get an upvote just by paying a certain amount.

And there are pragmatic reasons for whales to be willing to participate. As this approach would be much more sustainable than the current one, they could expect good ROI not just because they'll get a good percentage in terms of STEEM, but because this becoming the norm is very likely to help the price of STEEM grow. And if you are a whale, a small increase in the price of STEEM could alone offer huge ROI. The current pay-to-gain system is unsustainable and is making the steem community worse off, less attractive and less stable. This means, it's certainly getting some people turned off and the interest in being a part is being lowered by that. This is bound to have an adverse effect on the price. If this is countered and high quality content is rewarded, this will surely bring in more authors and more investors willing to profit from a growing and expanding community. I think if this point of view is presented to whales on regular basis, they might actually come to the realization that supporting sustainable practices will get them a higher ROI than supporting practices that undermine the integrity of the platform for immediate gains.