Why not something as simple as a self-vote drains your voting power exponentially rather than linearly like a regular vote, this would do a lot to curb behaviour.
There are the obvious self-votes, and there is covert self-voting - like delegating or giving away steem power to a bot that will always upvote your own content, having agreements like "I always vote for you, you always vote for me" with other account holders of the same size, etc. I think it's not good to promote the latter.