in a combat sim, I'd like to be able to be the general and control all the forces.(you think its been done?, just wait)But you could be able to fight as an individual in the campains you start. for example, if you were in control of D-day, you could plan the whole damn thing, and then be able to be on the LCT/C-47/fighter/bomber.
It could be based on history or a new war. or you could be faced with a problem, you fight the war, then you deal with conflicts following that war. EX-WW2, then cold war, korea, vietnam. a sequence like that