I think that Fallout multiplayer would be great. 32 player capacity would be awesome. BUT not as a MMO kind of thing. It would be great if players can set up sessions privately without going through Bethesda, and can connect to each other if they have all the same mods and stuff.
More fun, more cooperative play, death matches, team death matches, etc.
Hell, allow clans to designate Clan buildings (editable by clan leader or permitted clan members only, and clan leader must approve of changes before it's pushed to clan members) and every player in the clan would get a copy of it. That would be so cool.
Then to make it even better, Clan wars. 1 Clan building on each side. The first one to destroy the rival Clan building wins. Or the typical Capture the Flag game (except instead of flags, maybe capture the holotape with secret information).