RH looking at a different solution "Stratis"
Asking about this elsewhere it looks like Red Hat are doing work on the "Stratis Storage Project" .
This seems to be a bit of a management system that will allow you to emulate pretty much all features of an next generation file system using existing layers (LVM, MD , XFS). But adding things like block level checksumming to MD/LVM to allow the equivalent of individual file check sums. The argument seemed to be to, building this in a single layers like BTRFS and ZFS is too hard. The layering allows you to make the programming/debugging more manageable. I guess the key would be communication between layers, bad block checksum tells XFS the file is corrupt etc.
They also seem to have some interest in "BcacheFS". A "Bcachefs" developer says there are fundamental issues with the BTRFS design:
"btrfs, which was supposed to be Linux's next generation COW filesystem - Linux's answer to zfs. Unfortunately, too much code was written too quickly without focusing on getting the core design correct first, and now it has too many design mistakes baked into the on disk format and an enormous, messy codebase "
Not sure the truth of this, I don't know enough about it.