Then can you tell me how to use the ubuntu GUI install to a ZFS encrypted root, without zsys, without grub but with a .efi packed kernel?

Or how can you mount the efi partition to new systemd location /efi instead of /boot/efi (ex: if you're not using grub) without breaking the install?

There are just too many choices for too many people. It's best not to play, and let it be a commandline problem. You rarely have to reinstall without another OS or boot media, so doing a chroot and copy-pasting the right commands (or rsync or untar a working master image) is just simpler.