lower inflation and faster powerdowns, have done nothing to increase the bottom line

They have done a lot to improve the design but there are still a lot of things to improve.

If the high sp accounts spent their time upvoting the zero payout posts

This is not scalable, you need every users to curate to handle all the posts.

If you introduce only negative voting for the high sp holders the animosity towards them is only going to increase.

Animosity towards them is caused by the huge influence disparity, give minnows power and the animosity will go away.