That still requires every app to have a bespoke updater. You just pushed the invocation to the OS. A better solution would be for the system package manager to

That still requires every app to have a bespoke updater. You just pushed the invocation to the OS. A better solution would be for the system package manager to allow programs to add their own update servers. Assuming the developers package their programs the same way the system does, this allows you to use the exact same update logic. Most linuxes allow this. Add a third party repository to you sources, and you can update their software with the rest of your system. Ideally, you would have a more locked down version, where you can restrict the permissions of a given repository; although I'm not aware of anyone that has done that yet