My thought was an underwater city much like the Gungan city from Star Wars. http://images3.wikia.nocookie.net/__cb20090611182820/starwars/hu/images/9/96/Naboo_gungan_city.jpg The battles would be almost exclusive to indoors. Movement/transportation would be done primarily through transport 'lines' or tubes and teleporters, much like the caves did in PlanetSide 1. Movement around the main base and outskirt facilities would be done using transport lines, and movement to other main bases would be done via teleporters. Depending on how extravagant you get with it you could include submarine vehicles. However I think they should avoid that initially. I would want fighting to be mostly CQB, since we don't have much of that now, but it would be easy to tailor the bases to whatever. My whole motivation behind this is the visuals. Underwater can be considered the most alien place to us land dwelling creatures and I think the underwater world of Auraxis could be made very cool. Whether or not you include sea life (fish?) or just impressive structures, I think the whole concept of looking out of a base and seeing an underwater world is awesome. If you have any other constructive suggestions or need some clarification on an idea please post. I want this idea to take off!