If apt and others could simply allow us (package authors) to construct a URL from which the binary can be downloaded, and then plop it into the user's PATH for

If apt and others could simply allow us (package authors) to construct a URL from which the binary can be downloaded, and then plop it into the user's PATH for them, this would not be a problem. (What I'm getting at is that all it takes to install a custom build of Caddy -- with any number of plugins you want -- is a GET request.)