The benefits you propose should be tiered, always promoting users to get to the 'next' level and should be tied to the value perceptions of Steemit.

1. So, for example, the more SP you have, the longer your posts stay on the Top 'category' chart. (this would require we had top-category charts), or something similar. Longer visibility means more potential for voting, therefore more potential gain. So the implied perception is that investing in SP may pay off with more votes in your posts.

2. What about showing/paying out to the 3rd (or 4th) decimal place. This would be strictly a perception change. Not requiring any real change of the monetary system which is in palace. Instead of $0.00 not changing after your upvote, showing $0.001 (or $0.0001 might motivate people, as they realized they did move the needle, even if a very small amount.