When I look at an "open" world game I generally imagine a very few games that actually meet this. Star Wars Galaxy, EVE, Asherons Call are my first picks. These worlds, are huge. But utterly devoid of activity in the way that a traditional MMO is. This is not to say there isnt content, there is plenty, rocks to mine, rats to kill, people to pirate, empires to mantain. In SWG we had entire worlds to explore, sites that maybe only an artist and a few people ever got to appreciate because it was so incredibly remote.
The majority of MMO's are theme or mission driven, the openess of the world is generally just a caged staging area cluttered with art assets to facilitate the feel of the biome. The gameplay is still very much driven by it's combat system.
Guns of Icarus isnt different in this respect, combat and team work make up the core of the game play. Adding trade lanes essentially just adds travel time to a skirmish map, thats a lot of assets to add, and a lot of time doing nothing. I'd be more interested in a static map with a series of zones where we have to battle are way through, not unlike traveling around on older map systems in traditional RPG games.
A good example is Fallout 1 and 2. Large map area to explore, but broken up into a series of different random event zones outside of cities. These zones purpose was to facilitate a staging ground for the eventual combat, or dialouge that would follow allowing the world to have some extra content outside of the cities.
I could see a series of content missions being built up like this. Good examples would be random events popping up on the map for players to join, like "Anvala under siege by pirates!" so you'd join the map with a series of other players fighting it out over the skies of Anvala. Scores would be kept, depending on which side won would alter the economy.
Possibly putting the city state into the hands of another governing force, making it so trade items need to come from other locations.
