It's an interesting idea, but I'm not sure that capping the rewards is something that should be left to the voters (if you think flag wars are bad...).
I still believe that the easiest solution is to limit your ability to upvote a specific account to 2 times per week: Upvote work as before (possibly with the two upvote options I mention below: a "upvote for money+rep" or "upvote for rep"), but you can't upvote a specific user name more than twice a week.
That means people who write posts or comments can be guaranteed some form of payment (through self-vote) without being allowed to spam the pool, while also limiting the power of people who run bots or circle voting schemes. (But still allows people the flexibility to up-vote posts in their interest/friend group ).
Also, steemit needs to get a lot clearer about how that reward pool works.
The problem is that people would just distribute their steem to different accounts and upvote them with these.
It still increases the effort required at very little cost to other users: an easy fix that should at least remove the low-level vote spamming.
People are always going to try and vote-spam: low effort=high payoff. The only way to fix it is to increase the effort (without discouraging others), or lowering the payoff.
The problem with giving users the power to lower payoffs is the flame-wars (or the current run of downvotes). Potentially a fix that is less likely to be abused is to simply cap the amount of the reward pool an individual can claim in a day/week/monthly period.