Also, are we considering btrfs to be reliable now?
It's the default for fedora, ubuntu, opensuse, cachyos, so i'd say yes, or at least it's feature set is worth it's "unstability".
Each has their own /root, and they share /boot, /swap and /home.
This would work just fine with mount points on btrfs, probably not on a regular distro as you can't usually customize them like this, but on a terminal based install like arch? not a problem.