Yes dependecies managment in general is a bit lacking in Defold, I found…
Like we cant have true “packages” that we can install with the name we want (like install defold-event in a myevent directory)…I know that’s a problem also because of lua modules (we cant require a relative path) and Defold URL system (everything besides components is absolute, so you cant have a “relative URL” inside a module…)
So this makes reusable package a bit of a pain. Choose your name wisely or you would not be able to use this dependencie with another one of the same name!
Another thing to change could be to split developpment dependencies and runtime dependencies. Their is a lot of extensions/editor script I would like to install just once in the editor, not for every project, because they are just productivity tools. Like many of editor scripts. You dont need them as runtime dependencies, so it is a hassle to reinstall them in each project. However the assets-store kind of decrease the problem (and I guess this is the first motivation to develop it in the first place 
)
Like a VS Code extension, you dont reinstall it in every repo!
We could have separate “editor-extensions” (install once in editor), “assets/prefabs-store” (copy once assets to your projects) and “runtime dependencies” (external API used in the code → should be installable in local package with custom name.
And define specific directories in a project that store editor-extension code and runtime code, so a library developper can clearly organise what is used for what. And at the bundle level, you dont have to consider editor stuffs.
So builtins defold assets could live somewhere there.