@pedronis can you please provide your opinion here?
We (some of the @reviewers) were discussing this request for some time today. On one side we provide a system-backup interface, but there are no restore capabilities available to support this use case. On the other side, granting write access to the various personal-files directories requested here not only allows for confinement escape, but also access to very personal or even sensitive information that can be store in those locations.
Even though the requested directories are limited, this looks like a classic confinement request (but backup/restore capabilities are not a supported category).
Also FYI @soumyaDghosh is applying to be a snapcrafters member.