Hello All,
Yes you can't play everywhere at once but there is definitely allot of 'want' for a open world as a base for large scale military simulations, being able to have engagements all around the world without having to painstakingly generate half the terrain would be a huge asset to games like ARMA series or even Civilisation games.
Atm allot of developers of war/combat games spend huge amounts of time getting the terrain right/comparative to real-life, all that time could be cut out. Only thing needed is to populate the region, and general clean-up.
Outerra is definitely looking to be a fantastic toolset for indie developers, interested to see how human character systems turn out, but atm the vehicle systems in place look quite impressive. One could make a game based on that alone (i.e. WorldOfTanks).