I believe it is only possible with distributions that produce an initrd image not with Arch.
I never understood the need for this kind of installation. It is like copying the live-image of a system into a partition and booting it off a modification of the bootloader for another system.

Obarun is gradually becoming more and more independent of arch but basically it is still a modification of arch-linux. Anything that is possible for installing arch is possible for obarun. If you make a separate partition and install base through pacman into it then you chroot and build a system you like. Starting X in a chroot is a little hairy but I am sure if someone has a need for it it can be achieved.
Not the same thing as frugal but relevant? The beauty of arch is that is constantly rolling. No 5' go by without upgrades.

Thanks, interesting. I wonder now "again" how tails really works.
The one thing I am not buying is the security part, if you are able to manually edit the initrd image and modify it what is the difference?
Encryption must play a big role in this, but so it does on every system that can boot an encrypted installation.

I gave up on security measures long ago, it is not worth my trouble. I wonder what the zfs experts here have to say on this issue. With the zfs tools and ability to roll back to different versions of a system then frugal must be useless. All you have to do is encrypt the zfs ...? storage ?? what ever they call the space that keeps the snapshots.