I hate to be Johnny Buzzkill, but despite some updated rendering and AI, this is still basically the same game engine they've been using for everything since Morrowind, and the Creation Kit will not likely be much different from the Construction Kits before it. A similar looking multiplayer client mod appeared early in Oblivion's life as well. I don't recall having seen one for any version of Fallout, but a quick googling gives back a bunch of results for multiplayer mods in their alpha version. Nothing fully playable on the first page. There is no reason to think that this will get much further, with or without a creation kit. It will very likely run into the same hurdles every other effort to execute that task with this engine has hit, which is mainly that the game was never designed for multiplayer, and making it behave correctly is a lot more difficult than it sounds. It's not like the Creation Kit will feature a checkbox for Allow Multiplayer.