I think you're unnecessarilly restricting yourself by a wanting a full disk btrfs, particularly if you want to use UEFI or hibernation.. why do you want to restrict yourself in such a way?One tip I can offer is to disable compression on your /boot subvolume. And disable COW on your /var/log directory.
See here: https://wiki.archlinux.org/index.php/Bt … _subvolumeIf you are going to use a MBR/GPT partition to contain a bootable Btrfs filesystem, remember to leave at least 1MB from the beginning of the disk to leave room for GRUB files.
Fix these.https://bugs.archlinux.org/Or contribute to the wiki. Or seed the latest iso torrent. Or rewrite a popular, yet slow, application in pure C and submitit to the AUR. Or Help out with user problems in and around the forum, etc.