@joshman In order to prevent whales manipulating votes, the best way would be to create a powerup period instead of powerdown. It would go that way: once you decide to stake, only some percentage(let's say 10%) of your steem becomes Steem Power every week.

Why this is better: It forces new comers to use the platform for a few weeks before being fully powered up. They can't have all the influence they want in one click. It also prevents the manipulation you were talking about, as they won't be able to constantly power up and down.
And finally, if witness voting is being manipulated before a hardfork, a whale would need to power up weeks in advance in order to get maximum influence, this would incentivize long term hodling for influence.

I still like the 5% burn purely as a sink though. Maybe 5% would be too much and no one would use it so it could be tweaked later.