Require people to pay some amount to Kickstarter itself to buy a "large funding credit" (a virtual currency.) That credit must be spent, along with whatever actual donation you make, if you want to contribute over, say, $2000. The credits also don't "activate" until, say, six months after they're purchased--well outside of the (legitimate-vendor) chargeback window.

>The credits also don't "activate" until, say, six months after they're purchased--well outside of the (legitimate-vendor) chargeback window.

Who'd buy kickstarter credit just to hope that in 6 months there would be an interesting project to support?

The thing that wins kickstarter buyers over is the ease of supporting it. This would kill it.