The biggest problem IMO is that you can't use this format with an empty address. And also SPV clients can not do this on their own.
Also for this:
(Precondition: Your address exists as a single output in a transaction that has ben cemented in the bitcoin blockchain)
The transaction can have multiple outputs too, you can just add a new number after that "3" representing the
index (
refAlso why not use QR code?
They are simple, easily generated, and have error correction built in.