I am not sure about how many of you are familiar with Mount & Blade series, but i think that you should check out the game. HOMEPAGE
It is basically a medieval war simulator with single player battles, multiplayer battles and a WHOLE LOT OF MODS!
You can make your own army, become a vassal, or create your own kingdom, be mercenary, be a criminal, siege castles/cities, loot villages and do a lot more things. The replay value of this game is over 9000!!!
Since you can mod the game, you can make the battles be large 1000 men engagements over maps 5x the normal size (normal size is about 100 consecutive players, about 200 total per each side), but only if you steal a PC from NASA. xD
And since the last DLC came out, Napoleonic Wars, the game has official firearms centered gameplay in multiplayer with up to about 250 players. Somehow i start to see parallels with Ace Of Spades... Don't you see something similair?