I was just about to write a comment to ask why it can't be done like this (using CAS / symlinks). So I guess it can. Are there any disadvantages to using ied over npm?

It's not fully stable yet. I tried a while ago, and after running into 3 showstoping bugs (and filing bugreports) i had to give up.

Great idea though, and it probably has improved a bunch since then.

This is one of the reasons why I love the JS ecosystem. You can even choose among a few tools you use to install packages from a package manager.

It does not support external packages from git remote url (github).

Update:

Looks like it is supported now:

https://github.com/alexanderGugel/ied/issues/7#issuecomment-...

Private modules seem to be an issue at the moment, but a PR for this is pending.

I used it successfully in a project and it even worked with native modules.