I can easily see a multi-theatre FPS, like the CoD games. WW1 wasn?t just the trenches as too many people forget. The variety
This hypothetical game could have four campaigns, spanning four separate theatres; have the player as a member of a different army in each one. One could be set on the Western Front, fighting as a British soldier in the trenches. You get to work on a variety of missions, like sniping, manning machinegun posts and marking for artillery. Then you get to taste real battle at the Somme. You manage to survive, although you do get to witness the horrors of war, including a case of a man drowning in mud. You also see the first use of tanks, which inspires you to volunteer to become a member of a tank crew. Your first tank level would be the Battle of Cambrai and the climax of the British campaign would be a large tank at Amiens, one of the first battles to use combined arms of armour, air power and infantry.
A second campaign could focus on the German armies fighting the Russians. It would start similarly to the British one, climaxing at Tannenburg, but by the second half it has become much more fluid, fighting in Eastern European cities like Warsaw and Riga. You also have to defend against massive Russian armies at Kowel. The climax would be the transfer to the west for Operation Michael.
The third campaign would be a Russian one, starting with the Brusilov Offensive. Here the player experiences the same mass attacks you experienced as the German, but from the other side. After winning a few battles against the Austrians, the game quickly turns into a series of desperate attacks against the German Army. At the same time you experience second hand the turmoil?s that Russia is going through, until eventually the climax is the beginning of the Russian Civil War.
The fourth campaign could be an Ottoman one, where you originally fight the British in Mesopotamia. You start by retreating from the British at Basra, before fighting them to a standstill at the Battle of Ctesiphon and the Siege of Kut, whilst hearing news about the Battle of Gallipoli. The success carries on at the Battle of Hanna, before turning for the worse at the 2nd Battle of Kut by the end of the game you have been transferred to the Palestine Theatre and loosing to the British at the Battle of Megiddo (also known as the Battle of Armageddon).
There, four campaigns with a wider variety of gameplay than simple trench warfare as everyone keeps coming back to.