an open style game either WW1, WW2 or the year 4000 would be good if depending on how you fight and your outcome in a battle shapes the rest of the war would be good .... or maybe somthing where you choose what building to place the MG or where to hide that sniper or mines, or even where to dig in and make a makeshift trench ....
also i wouldnt mind seeing somthing simlar to americas army where for example on the hardest dificualty you have to qualify to be able to use particular weapon and features such as even the pistol/ smg/ rifle/ grenade/ explosives/ stealth tactics (sniper)/ medi packs/ air strikes/ morters strikes/ even to be the squad leader, and depending on what you pass you have access to, so if you dont become a leader for example you have to follow the other guys but you may have more fun hiding in the building with the MG insted of hanging back giving orders and calling in the air strikes...
it would be good if to become a medic you had to pass a medic course like In AA, or to become a officer you have to do some sort of officers training (target ID's, squad commands, tatical training, map reading (arty strikes) even basic language skills... i could go on for ever
dam it would be soooo good
EDIT: i just had to had to become a sniper you had to pass tests in where you needed to understand how to shoot ling range, like bullet velosity/ weight/ coefficentcy, distance of the shot, elevation, wind drift, angle of fire, temperature, humidity and even the effect of shooting through a mirrage .. (i only say this because i had to learn all this to shoot my .223 past 1000 yards all with a 2 second flight time, how cool...