Nice, but not possible.
Valve has not released the source code to the full game, just the libraries that contain the game code. The launcher would need to be modified, and the code for that still belongs solely to Valve.
In other words, it's impossible to make a Half-Life mod completely standalone. After all, it is a mod. If the team could do it, I'm sure they would, but... they can't.
You can run any HL mod on WON, the old network that existed before Steam, but you'll find little to no support for it. As for not needing Half-Life installed... you do need Half-Life installed, so I think you may be a little confused there.