I'd be great only if the game included the following:
Huge Land area
Major Conflict (2+ Major Power, 3+ Minors)
Real World Objectives (Capture town and Hold, then move up)
Balance between far away respawn points and getting back into the fun quicker
Huge dev 'event' say armoured NPC column is approching city B.
+
Real-world weather (Flooding, snowing, hail etc.)
Just imagining a small country with a massive capital in the middle and 4-5 major cities spread out as well as a few town/townships around them and each player faction has a homeland city and each one is fighting over the capital to insert either his or her's ideology whether Political or not. It'd need crazy server technology and alot of other power to support such a huge map with players etc.
Then to make it interesting having supply lines for producing vechiles of war, ensuring that other players may 'snipe' these convoys delaying or destroying any chance of adding vechiles to townships/cities and ensuring that players of the faction actually protect and guard them. Not to mention mines and stuff would need to be protected as well as civies etc, but it could be awesome, although many games could have been awesome except fall on thier face so bloody hard.