I am not sure anyone has really sat down and thought this through enough. I understand you Want more people downvoting excessively rewarded post. I get that. Reality bites. Look at the number of minnows and redfish. have you even looked at the number of daily active minnow accounts? have you added up the total SP power (thats the vote power they all have) and seen how much of a monetary effect they can have on a post? A few minutes of a check on trending - largerst with a small scroll is $217.62.
Reality just how much of an effect on that post would all the minnows have? Do you think that all the Daily Using minnows could really make a dent in the payout? Get real people. My 100% downvote would be $0.03 cents. At the bare minnimum of dolphinhood my downvote would be $0.10 cents. You would need 2170 I just became a dolphins to bring it to $0.00. Or 7233 minnows that are able to cast a 3 cent reward.
Like @jrcornel has pointed out, all it will do is increase bad apple trollish behavior and drive more people away from the steem blockchain. I understand that it is already a done deal, that it will be done that there will be a downvote pool and there is not a thing anyone on the blockchain can say to change that. At least take the precaution of requiring a comment before being allowing a downvote to go through.