I don't think we can directly reduce self-vote/curation returns of autovoters at the blockchain level, it would become kind of messy.
I also thought about it, it would be messy, it could generate complications that would affect us all.
But I think the second way to increase the rewards could come from the DHF or author (you have to determine the one that generates better results) is easier to implement and manage in the short term to incentivize and reward manual cures and the creation of quality content.
You have touched precisely a nervous and worrying point: “a lot of autovotes are just bloat and we the manually active ones are carrying the weight of them more often then not getting the same returns as us”.