Thanks for the info, it’s long time ago as i have tested Timeshift, then one point of my above statement is irrelevant.
Another way i make rollbacks
sudo mv /btrfs/@ /btrfs/@snapshots/old_root
sudo btrfs su sn /btrfs/@snapshots/root/15/snapshot /btrfs/@where /btrfs/@snpashots/root/15/snapshot is the currently booted ro-snapshot. This save the damaged subvolume, now as snapshot in @snapshots. You can even exchange @ from a running system (started from @), and reboot or remount into the new setup. Last case i tried self and it seemed to work properly, but would not trust it eighter 
The nice thing with this way is that any setup/config of FSTAB, GRUB, initramfs and kernels that’s stored into a snapshots remains correctly after rollback of @. You need only to know that in FSTAB we have to work only with subvol=@ mounts, not subvolid=xxx mounts. After a genfstab >> /etc/fstab we have to edit these mounts. There is only one point to consider: any later changes on partition, UUIDs, mountpoints and so on are forbidden, because we break the system configuration stored in our snapshots.
A small script started on boot from a ro-snapshot, selected in GRUB, could do this Rollback automatical and reboot the machine. Like we can when GRUB start the UEFI Shell.
This script maybe ask the User if he wish to start the CLI or Desktop Environment or want to rollback the system and reboot. I think thats a small patch on grub-btrfs script.
But you’re right, the problem are the toolchain, in any case some small changes are needed to get a system which can be presented to common users, with small knowledge of BTRFS. But, in longer timescale the user have to learn BTRFS. I remember my startup problems with BTRFS, the biggest one at beginning was: “how fu…ing should i setup my BTRFS layout ?”, “Have i to exclude /var or only partial like older suse setup with many subvolumes for /var ?” And on these question Manjaro Installer can give advise.
“Calamares can now handle swapfiles with btrfs automatically per user setting. It uses the @swap subvolume”,
good to know, i use architect or easily clone my systems with rsync. Last time i tried calamares i must overseen this feature, or is it new?