Something similar is actually implemented in Ecency - you can buy exposure with their Points, so it is sort of paying the frontend for "reblogging". Sure, it is not the same as being reblogged by someone whose target audience is more likely to actually consume your content due to aligned interests, but in the same time the actual reach is far bigger (sort of a difference between viral marketing vs general ads).
The problem is that there is no financial incentive to reblog someone else's work.
There is, although not very strong. By exposing reblogged content to users who didn't see it before, there is a chance they will upvote it. Assuming you've also upvoted the article you've reblogged, if those new upvoters vote outside of optimal voting window, part of the curation reward they "generated" will go to people who voted in first window.