I have been working on exactly this with Filestash (https://github.com/mickael-kerjean/filestash), out of millions of users, 99% of them don't seem to care so much about the malleability, it gets very usefull when a company ask for something that 99.99% of people don't care without having to add yet another setting toggle. A recent example was when supporting gobd compliance deployment which required us to sign logs via a vendor who can deliver a qualified electronic signature for which nobody outside Europe would care about