Change the entire look sound and feel of the entire game by making it a Ghost Recon style squad based tactical stealth experience so that orders can be issued to three other AI teammates who could alternatively be controlled by other players. Look for tons of new vehicles, equipment and weapons break them down into light medium and heavy categories with the help of military, weapons and hand to hand combat experts for use in the open worlds of the Pacific and Eastern Fronts.
Think how in or out of vehicles players will be experts at navigating, traversing and exploring on land, sea and air.
Do detailed research into both theatres mentioned above and let it show in the types of special ops and unconventional forces and warriors operating in them, whether they're Partisans/guerrillas, Spetsnaz Naval Commandos, Chindits or Alamo Scouts among others and how they worked together against the enemy.
This will help when looking for ways to avoid the enemy as the guerrillas and partisans knowledge of the terrain will be able to show and guide players along stealthy routes to stay hidden and great spots for coordinating ambushes, observing and spying on enemies to gain information.
Any information or observations they and other teammates provide will appear on players maps.
Also the firing ranges from previous games could be part of and based on famous bigger training camps/bases for learning the various new skills required and that the game will include to improve players' attributes like stamina, endurance, conditioning, strength and speed so they can move faster and hit harder for longer without getting tired easily.
The longer they use particular weapons vehicles or characters the better they'll perform and more proficient with them encouraging players to invest time in customising them.