I like this 'region experience' idea more than the 'troop morale' idea. Troops gain 'region experience' because they get to know the territory when fighting. Generally it's a way to simulate that your troops have more chances to backstep your enemies, for example, but the gameplay is kept simple. But if there was something like troop morale, the player would must have possibilities to rise the morale by getting better support, for example and therefore the gameplay would become more complicated, but a game should be as simple as possible. And about this "the crew of a vehicle has a chance to survive when the vehicle is destroyed"-thing: I think it's not really necessary, but it's the simplest way to enable basic infantry to enter vehicles and these vehicles gain the soldier's experience, for example. If a vehicle gets destroyed, there is a certain chance that a basic infantry with the same experience spawns just next to the destroyed vehicle.