I wonder if this could be used instead of image based computer management for enterprise settings. Basically the team managing the systems have some settings, employees have their own overlay (to account for personal preference in tools or directory structure), and then you just install the entire machine at the start of every day.
It seems really complex though, so I'm not entirely convinced it's a good idea.
How would this work from a bandwidth and caching perspective? I'm thinking it would be problematic if hundreds of workstations need to download gigs of software at 9am every morning.
At least for nix you can set up local caches, so this would save most of the bandwidth. But you could also just keep the /nix/store folder - as it's an immutable store for all the packages.
It seems really complex though, so I'm not entirely convinced it's a good idea.