I think a great way to tie in rewards is alert the person on payouts what % each reblog contributed to the payout. That way the author has information they can choose to act on and send tips or w/e to the reblogger. At least I think that would be possible with the reblog info added to the chain in vote data under memo maybe.
I have a recent post talking about a reblog rewarder idea that may have touched on some things you mention here if you wanna check it out.
The biggest issue is always how to prevent abuse, spam or other incentives that go against the main idea of reblogs cause there's rewards involved. I think this idea wouldn't really bring out the bad things.