Arguments for app launchers in the dash

It would be extremely useful for power users if one could apply arguments when launching an app from the dash.

For example, I hit 'super' and type "firefox". I navigate to the Firefox icon using the arrow keys, and push another key - perhaps tab could be used? This would open a text entry field of some description, into which I could type, say, "http://www.launchpad.net". Pushing return would then open Firefox at the specified address.

This would not be difficult to implement in the backend, as it would simply involve appending the arguments supplied onto the end of the command used to launch the application.