No because this would tie the gift card to an identity

No, because email works fine. Some must use it tho. Like a throw away npub account. I won't tho. I like email.

If I can pay with XMR I think that would be interesting (as one can just create a new Nostr key for retrieving the card) 🤔 Let's do it! 🔥

Hell yeah. GOAT move

No, but if you delivered me gift cards to my noster paid with Monero, I'd use it.

Yes, worth shipping. Just build it on NIP-17, which supersedes the old NIP-04 DMs. NIP-04 is deprecated, and it exposed who is talking to whom, while NIP-17 hides that metadata.