Hi! I work at Stripe.
You're indeed right about both of these use cases -- we've actually built the first one (but didn't post about it). On your settings page, you can go to Emails and you'll find a preview of the receipts. There you can click "Send test receipt" to any email address you'd like.
Your second point is also something we'd like to build, especially something like including metadata from a charge on the receipt.
We'll definitely keep your suggestions in mind!
* Receipts in the test environment, sent to a per-account "testing" email address
* The ability to set more customer information to be included on the receipt. For example, some customers want their address, phone number, VAT number, license ID, or cat's name on their invoice.