> Since transoceanic travel is going to be impossible and long treks over land nearly so, perhaps we should consider localizing to a continent, if not a region, for maximum player interaction?

Traversing the sea will be much easier than traversing land (as far as the dead are concerned, anyhow). I'll add a little comment explaining that the dead make poor swimmers, and that zombie sharks have a hard time biting through metal hulls. 

Planes still exist, to those who want them, although fuel procurement will be heavily handicapped by the world wide collapse of most modern industries. So there'll be that option. Again, I'll add a little section detailing what kind of technology players can expect to have access to. Common sense pretty much applies; yes, Modern stuff is still very much available, but the more sophisticated it is, and the more expensive it is to run, the less of them there'll be. Plus, after the fall of the world, the survivors may have come up with "better" ways of living and fighting.

Satellites still orbit Earth, enabling those with the equipment, resources and the know-how to "hail all frequencies". 

I want to keep the world map, to vastly increase the amount of cultures people could come up with. I feel either an American, Middle Eastern, European or African localisation would restrict the types. Perhaps I could split the map into the main geographical theatres... hmm, I'll mull over it. 

Thanks for the input though, questions, suggestions and comments are always welcome.