Contrary to the popular oppinion, externals are actually realistic and should always be enabled on 169th server.
Both US and Russian Airforce have been using pilots with special, RL tested capabilities of "remote viewing". They could see things remotely, enemy bases, enemy personel, missiles and even enemy jets.
This is why ED enabled this unique capability in LOMAC. With a press of an F2 button you get to be one of those special test subjects, with special mental powers.
In my oppinion, any serious squad/server who holds dearly to its reputation, should be having the externals ON, all the time.