On the A320/321 I fly, we have two choices, turn on brake fans if fitted or wait for the temps to reduce on their own, on the small bus they don't heat up on the taxi out like on a wide body. Also, in the book it's called a takeoff limitation, we do not have the option to takeoff and let them dangle, now should we have a brake deactivated (brakes disconnected fo spotters), we do delay retraction and take the appropriate penalty, other similar MEL requirements also. My guess is that one or two of the brakes were capped off on the A340.