I'm developing a set of open source tools that aims at establishing a standard way of transmitting transaction for Stellar ecosystem. While QRs is not the primary focus, it is definitely part of it. The protocol is called Cosmic Links. Did you tried it Neil?
If you want a taste of it :
Any Stellar operation is supported, including multi-operation transactions. You can pass XDR as well using:
You can add support for cosmic links in your own tools using the library. You'll also find more info in the docs.
Please note that's I'm going to release the beta 2 around the 15th with new features, partial sep0007 support and syntactic changes, as I'm heading toward the stable iteration.
If it is what you need, you can also clone of the cosmic.link website and customize it to your needs. While I didn't released the doc to do that yet, I'm willing to offer support for that operation.
If anything I'm avalaible on Stellar Slack (@mister.Ticot) and on the cosmiclink telegram group.