I suggest you take a look at Planetside 2's way of dealing with 2000 players on one map at the same time. They pretty much only load the players who are in your area.
Territory-control and capturing territories is also something interesting in PS2, have a look at it.
Lastly, something I think the devs of PS2 have incorporated very well in their game is to make specific parts of the map more wanted at random times, PS2 does this by giving you more resources if you capture a specific part of the map at a random time, this concentrates the battles more and makes for more enjoyment.
Could you specify more on perma-death? I hate losing my progress and I usually GTX if the consequences are high.
