In combat, out of a main battle tank's crew, only the commander has any practical situational awareness. The gunner is glued to the main gun sight and will be attempting to hit the one target he can see. The loader, if there is one, is entirely preoccupied with the physically demanding task of reloading the main gun. The driver is low in the hull so has a poor vantage point, and will either be moving the tank or standing ready to do so. The commander can actually look around a bit, call out targets to the gunner, give movement orders to the driver, and potentially communicate with other tanks. At the company and platoon levels (squadron and company for the British) the tank commander may also be a small unit commander.
If a main battle tank or similar vehicle has no commander, then either someone else has to step into that role or the crew will have very little awareness of the situation outside the vehicle. If the vehicle is being crewed by PCs then the referee should give them almost no information about the outside. If the vehicle is being crewed by NPCs then it may well stop fighting. History has shown that when an AFV takes a crew casualty, the remainder of the crew is very likely to drive away from the fighting.