I sympathize with your concerns for stability and testing, but I think that you might reconsider things in open-source ZFS land. OpenZFS/ZoL have been merged since the 2.0 release several years back, and some very large (e.g. Netflix) environments use FreeBSD which in turn uses OpenZFS, as well as being in use by the various Illumos derivatives and such. It is true that there has been some feature divergence between Oracle ZFS and OpenZFS since the fork, but as I recall that was more "nice to haves" like fs-native encryption than essential reliability fixes, fwiw.
Don't disagree with your post but netflix doesn't use zfs for a couple of reasons, one of which is broken sendfile support (though that might be fixed soon!).
