The turret living-dead

[Soldier]

You're obviously speaking of the tank commander being badly wounded or killed by a snipper, shrapnel etc...
In that case the "gun loader" is a perfect choice for the job of observing the surroundings and spotting for enemy threads, etc.
With the officer (if killed) missing, the tank crew ceases to be a team. (very important point to consider)
When ever such disabled tank gets involved in a firefight, awareness of it's environment, drops considerably. With the loader back at his designated function..