Another solution is making Steem Power depreciable so that whales had to generate good content to maintain or increase their power. If you upvote, a portion of your Steem Power converts into reward to an author. If you don't upvote, the Steem Power depreciates passively. So it will be about "velocity of power", which means that the monetary framework of steemit will favour authors who continue to deliver high quality content.
Like in the real economy, the problem is not concentration of wealth itself, but a lack of real competition in achieving the high ranks. If those on the top are people who had and have been working hard to get there it is perfectly fine.