It has so many interesting possible applications. Declarative and reproducible wine configurations for games and software; universal (cross-distro) packaging (without emulated runtime environments like flatpak); reproducible user environments managed easily with a GUI with trivial version control (both for config and software versions); pre-configuring a system before even setting it up (such as configuring a raspberry pi before you’ve even bought one so that once you have, you just install and configure everything in one go).