Sounds reasonable. There is a risk of people downvoting in retaliation at the last minute, but they cannot do too much of that. Changing an upvote percentage should not give you more curation rewards.
So far a lot of the bigger abusers are being dealt with on Hive whilst they continue to milk Steem. I look forward to the Steem price plummeting as it's sad to see them profit from all that crap.
The risk of people downvoting at the last minute will drive free speech out of Hive through censorship.