Right, wallets should (though I don’t know about currently) support either setting the payer_note or signing a message with the payer-key as a part of generating proof-of-payment, both of which would suffice. Definitely need to spec that part out and make sure wallet support it as a part of the BIP 353 payment proof logic, but I don’t think exposing BOLT 12 invoices outside of the LN wallet makes sense.