root / on overlay fs

It caught my that Live Edition mounts root / on overlay file system. I read a little about it. Now I am having idea to use such solution in hardware installation. I think it can be particularly useful for -current users. Making things simple: you need two partitions (file systems) - they all together create overlay. Lower layer is read-only. It keeps your last stable snapshot of -current. Upper is where all updates go in. Once you are satisfied with stability of such system - you merg both layers and push into lower layer. Which creates new stable snapshot of -current. If update breaks system - for time being you have all lower working stable snapshot. So there will be no situation when update can make your computer useless. You can always run latest stable snapshot. It is also useful for people building own packages. Just every external package goes to upper layer. I mean this is solution for stable system. Having multiple layers allows dynamically change system configuration. Just no need to remove packages physically - only layer there exist on.