pledge

I'm interested in being able to set up a pledging system, that can enable donation bounties as a content type, and allows people to first pledge, then be billed if pledges reach a capped amount, or have no one billed of pledges do not reach an amount.

Is it already possible to do this with existing modules (like e-commerce and cck)? If not, I am committed to producing this capability, and would feedback from this group on suggestions about how to approach from a module creation standpoint