When KaOS started in 2013, there was some serious consideration to base this distro on Illumos. One of the biggest draws for Illumos was the ZFS filesystem.
ZFS has been possible on Linux system for a few years now, but licensing issues and no installer support meant it was not an option to use in KaOS.
Today Calamares received initial support for ZFS, and licensing issues should be no problem if the needed modules are not build into the kernel, but distributed as separate modules instead.
For now, the only kernel that supports ZFS is the linux-next kernel, since dracut is fully supported by ZFS, anything mkinitcpio based needs to come from downstream.
This also means, the move to dracut as default initcpio needs to be finalized, it has been default for linux-next since March, with no issues found or reported. Biggest job for that will be the ISO creation, rewrite section to use dracut. The stable linux kernel move is simple, it can use the same settings as linux-next.
ZFS packages now in the repository: