Some of my concerns:
1) Authorize now but only charge when actually shipping is standard Visa policy. Doing it any other way is not allowed. Your system seems like a workaround for that, which raises my alarm bells.
2) To be clear - you are storing the credit cards in your vault (not Stripe's vault), and then running them through your Stripe account later as normal transactions? And this is cool with Stripe/Visa?
3) What do you mean PCI compliant? Do you think you are, or are you being regularly audited? Where are your servers? Credit cards are serious business; we need to know.
4) I'd expect a ton of chargebacks. How are those handled? What do the chargeback fees look like?
5) Is this Amazon Payments without the branding?
I want to love your product, but I wonder these things. Please help me understand!