> A much better way forward would be to implement a truly transactional and functional packaging system (a la nix/guix), where updates could be rolled back seam

> A much better way forward would be to implement a truly transactional and functional packaging system (a la nix/guix), where updates could be rolled back seamlessly. It doesn't work like nix/guix, but Ubuntu are doing what you describe with Click and Snappy. Click is already live on Ubuntu phones.