Use [command]-[return] for shortcut My Problem

On my Mac I would love to emulate my Linux development workflow using key-binds. A core part of this workflow is that when I press [super]-[enter] a new terminal window opens.

My Attempts

I have an automator service that opens a new terminal for me, whether or not my iterm2 application is running.  I am trying to assign that service to a shortcut using instructions found here.  Unfortunately, I cannot seem to assign it the shortcut that I would prefer, which is [command]-[return].  Am I missing something? Is this just not supported, or is there a workaround that I could use?
Unfortunately, one cannot assign ⌘↩ in:

System Preferences > Keyboard > Shortcuts > Services

However, one can assign ⌘↩ in FastScripts.



Note that I am not affiliated with the developer of FastScripts, just a satisfied user of the product.