8. Optional Local Co-Op
It divides people every time it gets brought up, and so to please both sides of the fence (and ignore the immersion-breaking existence of online multiplayer), Bethesda should go with local split-screen co-op for certain missions - as well as simply letting you not bother if you don't want to. There has to be something in the newest Fallout to set it apart from the rest, and introducing this component to the design would be a very immediate way to set it apart. In addition, hardly anyone does 'couch co-op' these days as they favour online instead, and considering how the only way to maintain some semblance of taking the experience seriously would be for you and a buddy to team-up in the same physical space to talk out strategies and tactics on-mission, it could be perfect.