So what if it were to happen again but with a huge open world RPG
It worked for Goldeneye, because it's basic level it was an on the rails shooter with small confined levels. Bethesda's games are a different kettle of fish.
If Bethesda did it for Fallout 4, I wouldn't touch it because having been added at the last minute it would be utterly terrible and broken.
As others said, wouldn't work. Only way you could have a multiplayer would be co-op dungeon raiding or a PvP game like NCR battling the Legion. Maps not an MMO you can each wander any where in the world so it's not workable that way.
No, no. Please no. We are called The Sole Survivor for a reason.
This should go in our open http://www.gamesas.com/topic/1512524-fallout-multiplayer-discussion-thread/