Earlier quoted context omitted.
You are broadly describing PPAs. Adding a package from a PPA is a three-line (easily scriptable) process: add-apt-repository , apt-get update , apt-get install . Obviously, that doesn't just work for PPAs, but for all apt repositories. Launchpad does some central indexing ("other versions of this package") for PPAs, but I don't think it's accessible via command line. There is no indication how popular a PPA is, but P…
You are broadly describing PPAs. Yes, indeed I am. The point where PPAs fall short is that the user still needs to add a repository when all he wants is to install a package. I maintain `apt-get install https://foobar.com/pkg` is where it's at. Feel free to query me all you want ("really add this untrusted repo?", "fetch updates from there?", "trust this key?" etc.), but by all means make it a one-liner. Not three, n…
I don't see why it'd have to be integrated into apt-get itself, which does other things. The next step would be to create this a GUI process and to integrate it into apt-url, to make it easy to install stuff from the web. Of course making it easier to install stuff from untrusted sources also makes it easier for users to install malware, which I recon is why they haven't made it this easy yet.
If you want to have the ability to pull updates, you need some location to query for them, and that location is the repository. Even if it's just for a single package. If you want to install a single package without updates, there's deb files.