These are some interesting ideas.

My idea would be to enable a function that lets you set all rewards to beneficiaries after a certain point.

For example if rewards > 10 SBD set beneficiary @steem.dao 100%

This would serve to purposes:

1. It would allow authors to set the desired value for their blog or post and gain a better sense of quality as their target is eventually realistic.
2. It would allow curators to better determine if a post is over rewarded or not and move on.

One could also incorporate it with your idea of changing the curation level or window accordingly. I can also suggest that we can even allow authors to set the curation window and whether it is diminishing or not or adjust it based on their average rate of curation so really popular bloggers can experiment and such.