I've had this in my head for a long time:

First person shooter war game, but you pick your side(nations to play as), sort of like battlefield 2, only spicyer.  The games creators will host all servers as well as make up the generals/leaders of the fighting nations( normal players will later rise to these ranks by certain skill in a battle and are promoted, allowing the game creators to resign, etc).  Then each day the leaders will email all players of the battle plans for the day i.e. where we are attacking etc.  And in the game you will see where the enemy is on the global strategic map , territories, etc.  And each day both sides will host a few battle over 10 to 30 territories, some battles taking place at the same time to meet the huge number of online players.  by the time this game can be achieved online shooters should be able to have up to 300 players in a single match!  And everyone has a rank and is assigned to squads and you fight with these squads or not at all.  so you get to know your fellow soldiers quickly, of course you dont need to be shacked up with complete strangers, you can create you own squad and invite members/friends.  Maximum # of squads a player can be apart of (incase all you friends in one squad is offline one day) is five, which also allows you to decide which battle you will participate in each day, do you choose to fight in sqd 1 now and in a hour fight with sqd 5?  all modern weapons and vehicles and get this the content will be updateable such as when you reach a new rank and you want a specific gun, you get to choose from a list online from a gun encyclopedia and download the gun you want(becuase lets face it you couldn't store all the guns on your computers memory so you only download what you want to use).  The only thing you computer stores is the all the guns visuals and statistics.

There will be infantry sqds, tank sqds, air sqds, and these sqds take up slots in you 5 sqd slots, so you can have all five be infantry, or tank/ vehicle or air, but you decision determines your playing for that squad, for example the infantry sqd can only be infantry, but can enter humvees, etc but not tanks or anything heavy, and if your playing a tank sqd then your stuck in your tank, you can bail out but you weapons avaible to tank soldiers will be small machine guns so dont think you can be in a tank at one pt and then bail out and be a infantry guy becuase your equipment will not stand up for long againist other "infantry sqd" soldiers.  And depending on which sqds people decide to play as in a match determines what vehicle classes participate, so if the US side is fighting in a teritory and the sqds playing are all infantry with one air then you gonna see alot of humvees and troops and maybe 3 to 10 planes in the air, while if the enemy has a well balanced selection they will have an advantage(good mix a troops, tanks, and air power.

And the game is realistic meaning if 300 players are playing each player gets only 3 respawns total if killed or none!  And damage is real if you get shot in the right spot (no armor) your dead, so its a game where quick accurate shooters win(real life.. boys). 

And so the nations fight it out unitl they have all the territories, and then start over....

So yeah............. its not fully thought out yet but the basic ideas are covered. its a little mix of strategy and fps meets massive online ongoing tournaments