That said, I generally agree with you in that do one thing and do it well is a laudable design goal. However, I also am very excited about encrypted ZFS for one main reason: backups.
Okay two. Snapshots and backups!
ZFS is absolutely amazing to use as a home NAS that does daily (or more) snapshots and then nightly differential syncs to a second location. In the past I had to run all my own infrastructure to do this, as the data was in the clear.
Now my ZFS nerd friend and I can simply swap backup space and have "zero knowledge" of the others' files, while retaining the amazing features of ZFS snapshots+zfs send/receive.
This also tickles the "create an encrypted ZFS backups as a service" service itch for me, but then I realize I'd be creating it for all 13 potential users of the service. That said, I'm sure rsync.net will offer this functionality shortly - which would make them a viable backup target for me.
It's just that majority of users never have reason to see more than tiny signs of the layers hidden behind (mostly) 2 command line tools, and for various reasons those layers are compiled into one one module.
But the clean layered design is how LustreZFS happened :)
I also recall someone working years ago on a way to push snapshots to S3 or similar, but I never heard if that idea got off the ground (downside is of course the snapshots need to be recovered before they can be mounted, but the dollar cost would be rock bottom).
What would be more interesting is a backup application for Desktop Linux that assumes a ZFS root; all the problems that plague Desktop applications (that seem to keep them in eternal beta or wither away) disappear. It needs to switch on and push snapshots. It needs allow the remote file system to be mounted (to browse the snapshots for selective recovery). It needs a a disaster recovery process to recover an entire system from a remote snapshot.
You can pipe zfs send to gof3r.
This is why I really wish btrfs would get native encryption, but maybe my info is out of date.
In my case, because it's what Ubuntu "supports" for bootable root crypto ZFS, and I wanted to try it.
I've run ZFS on top of LUKS for my backup storage servers for probably over a decade now, and it works fine. But it wasn't really an option for my workstation.
That said, I'm not really sure what benefit I'm gaining from ZFS on my desktop. I've got that snapshots which are definitely nice. I've used it a couple times to go back in time. In theory I can go back if I wedge the system through package installs or an OS upgrade, but I've not done that (yet). It does slow down package installs because of taking snapshots, but that's ok generally.
And in my experience LUKS works great.
