The more times a story gets submitted, the more upvotes it generally gets because more people have already read it. No matter how good a story is the odds are that it won't get past the new page simply because there aren't many people willing to triage stories. And by the time those who see a story in the new queue finish reading it and vote on it, it's often already too late for it to make the front page. Whereas lots of people are happy to vote for a story they've already seen.
Since stories usually hit the front page when their score is around 6, I think it would make sense to give the first five upvoters a share of the karma from the submission. (With the submitter getting the most, and the first upvoter getting more than the fifth.)
It is a good idea, but I feel that your first-five-upvoter share is too strong of an incentive. It will encourage upvoting for the sake of karma rather than to reflect the overall quality of the article. There could be up-vote spam. It could also come in the form of vote herding on the new page because once an article has 2-3 points, there will be a rush for the remaining 4-5 slots. The result is a more cycled-through front page with worse quality articles.
Ha... so you need give people karma if they voted early (in the first 5) on an article that becomes popular, and penalize them for voting early on an article that goes nowhere once it's on the front page.
It would be simpler to just give the first 5 or whatever upvoters a bonus based on the total upvotes the article receives, if someone decided to do something like that.
Since stories usually hit the front page when their score is around 6, I think it would make sense to give the first five upvoters a share of the karma from the submission. (With the submitter getting the most, and the first upvoter getting more than the fifth.)