Honestly, my favorite idea is that Steem Power and witness voting was a simple equation of stake amount * stake length. Why would this be good?
Let's say someone from Venezuela can only afford to purchase 500 STEEM to power up, while the average person on Steem can afford 5000. The poorer person could have an equal amount of upvote/downvote potency and witness vote potency simply by being willing to lock up their stake for 10x as much time as the average user.
In this system its not just about how much STEEM you lock up, the longer you lock up your STEEM the more influence you have over the blockchain. This could be very good for the price of STEEM because a lot of STEEM would get locked up for very long periods of time, but it would also be a much more fair system.
For example, let's say a person had 50 STEEM and was willing to lock it up for 10 years. They would be equally influential in the network as someone with 5000 STEEM locked up for 36 days and 12 hours.