Maybe a viable option for single-application container images. They would on the one side offer the ability to have tight control around used functions (to allow for missing features) but also be able to exactly target an FS and be optimized for it.
Containers don't control the FS that they're written to. A container image is in the tar format and at runtime the underlying FS is defined by the host, which is why containers only run on hosts with union filesystems
