Could Elixir ever support a good plugin system and wouldn't it be awesome if it did?

[kokolegorille]

Yes it is possible, but I remember some previous warnings doing this

How to create a sandbox to run untrusted code/modules?

Unfortunately it is still possible, and quite easy in fact, to load a module into the system. Even if you were to remove the code module the basic BIFs are still there. You would need a very very controlled access to stop this. And I still wouldn’t trust it.