What does the converted report look like? I ask, since dear Aunt Fannie is so proud of her forms?
My question is, why are those who fear better transparency with the system? It does not stop or even slow down the free market system, it only allows for it to work properly with all parties being more accountable.
I don't think a single vault system will work either. I was thinking more like 50. A nice round number.

I don't know what it looks like but someone used an analogy while we were discussing the issue.
It's a working document, similar to a client making a xerox copy of the report, tearing off the pages that didn't interest them (photos, coversheets, TOC's, transmittal letters, etc.) and then marking it up in red pencil.
No one is under the impression that this is what the appraiser sent.
Appraisers are not interested in such systems. They can do it now, they bear the cost and they could have been using it for years. Such systems take away the ability to blame others for their own shortcomings.The digital signature would apply to multple recipients. There is nothing restricting it to just the first recipient.
Good digital signatures not only verify the security of the report, they also verify the authenticity of the author via hardware. This can be done using a "token," usually a USB fob. The token must be in the computer in order to apply the signature.
Someone could change a report, but the digital signature would alert the reader that the file was altered. Someone might apply another digital signature, but they could not apply yours.
Anyone can Google "digital signature" or "PKI Signature" and see that this is widely used technology.