This is generally a good idea, although there are some issues surrounding my mind.
The first issue with this system would be estimation process. How would the system estimate If a user is using liquid SBD or STEEM earned from Utopian contrubitions to power up, rather than Its own investment (or liquid assets from other posts rewards). If there will be no distinction between them, I fear that this new system will only benefit high SP users.
And this is a second question mark for me that will lead to another problem. Although this system encourages users to do Power Up, I think that new users would be discouraged to contribute to the Utopian system because of possible low awards.