I've been thinking about these problems, I think for one thing there's no reason why you couldn't continue a campaign for more than 7 days. The hardest part would be keeping track of who upvoted or transfered how much.

Still, with apps like steemitreports you could break down # of upvotes and amount of steem over the course of however many days you want.

We'd have to adjust how the rewards are given, it wouldn't be exactly like kickstarter. For example somebody who upvoted several times for a total value of 1 cent, would maybe be eligible for a 1% upvote from the person raising funds, but you obviously wouldn't be sending them a signed poster or something