Personally i am extremely opposed to the idea, mostly because i find it far to likely that it will be to much like a standard MMO with a Fallout skin (lookin' at you ESO)

I have always liked the idea of just adding in the possibility of playing alongside 1 other player in the overworld and adding small game type-esk play modes for larger online aspects. In fact the lore for Fallout could really lend itself to this kind of lobby with VR pods in current timeline, or with training modules used by Enclave or Brotherhood somewhere. Be able to literally walk into arcade-like caffes and enter the online lobbies by entering the new, smaller world space.

From what I remember there was one in the works but it was cancelled. I'll have a look and see if I can find anything out and post links.

en.wikipedia.org wiki Fallout_Online#Legal_dispute_and_cancellation
Had to remove the "/"

The big issue with me and MMOs is that they pretty much stick a foot up the ass of modders and mod fans. A lot of modders put armors and weapons from other series and IRL into Fallout (and everything else, but we're just sticking on Fallout for the time being), which wouldn't fly legally, of course, but modding is a non-profit community pastime that makes the game feel more original and gives it more personalized content.

That doesn't matter worth a damn to the developers of a hypothetical "Fallout Online".

I'd be tickled pink if there was a cooperative version of Fallout 4, where you could journey around with a friend provided that you have all the same mods enabled (of course). I heard there's something like that for Skyrim.

Yeah, there are mods that allowed multiplayer for Skyrim, Marrowind, I think Oblivion and I think theres one for New Vegas, but they are all very buggy and from what I understand only work over a LAN connection, I could be wrong about that though.