Roger,
Yes we have a (patent pending) solution for handling C2PA-signed photos that is unique to a metadata-editing workflow which is Photo Mechanic. I did a short presentation at last year's IPTC Metadata Conference that describes the basics, and we have been working with Sony and The Associated Press for some time with a special beta version of Photo Mechanic.
As you may know, the C2PA specification is still in flux and the Content Authenticity Initiative's SDK that we use is in beta. We are waiting for parts of the C2PA spec to be flushed out (e.g. TimeStamp manifests) and is implemented in the CAI SDK. Until then we are obviously in a beta mode.
We are still working on certain aspects of signing and then we will likely open this to additional beta testers by invitation. There is also a lot of documentation that needs to be produced because it does slightly affect the workflow. But for the most part, Photo Mechanic can be used in its myriad of workflow variations with an additional step to sign photos before they "leave the ecosystem" (not unlike a C2PA implementation in a pixel-editing application like Photoshop).
--dennis
