I hated the idea of mixing multiplayer into my single-player Bethesda game. Then an idea, spawned from a completely unrelated concept came to mind.
What if Co-Op happened with one character playing as their own Avatar, and the second player took command of an active follower.
Obviously, this would require a few things, like a matching plugin list (including versions) though not matching textures/meshes.
Its an idea. Maybe not a good one, but it could allow for a few interesting things.
A lot of potential fun (and longevity) for people streaming their games, allowing them to have a live friend on screen.
Meet those occasional calls for multiplayer without turning our game into Fall of Duty, or a Fallout MMO.