You could hide all that from the user, users would only know npubs. Otherwise maybe you can have a look at paynyms in bitcoin, don't know the inner workings but maybe it would be possible to use npub instead of a paynym code.

Would be more useful to accumulate Sats for someone not yet on #nostr. Usecase: someone’s external post gets shared here but they’re not on nostr. They can join and collect those Sats

When tipping people that are not ready to be tipped by bitcoin I usually shared private keys with them, together with a disclaimer that these funds may get taken by me if they don't use them within 3 months. I printed that on paper wallets and so far I did not take any back but I fancy to believe I ...