The problem is, it's not enough to have a transactional filesystem as it will inevitably have a different API, one that is not POSIX compliant. Also, you can't

The problem is, it's not enough to have a transactional filesystem as it will inevitably have a different API, one that is not POSIX compliant. Also, you can't jut make the filesystem transactional, in the end you also need an entire transactional OS built around it. Some years ago I set out to eliminate the accidental complexity and kept removing parts of the system that caused any specific problem. In the end, the filesystem + OS turned out to be the biggest culprit.