Give me full crew functionality such as con reports and auto gunners and then we'll talk.
Press a button and in 8 milli seconds you're in the tail gunner position. Take 3 seconds to scan the sky behind you from deck to 40K alt, and 4 miles behind the plane.
Press another button and you're in the top turret for another 3 seconds to scan the sky above the plane.
Press another button and you're in the ball turret for another 3 seconds to scan the sky below.
Press and you're back in the pilot seat.
9.024 seconds to get complete spherical awareness of a 4 mile radius around the plane. There isn't a crew that ever flew any bomber that ever exsisted that could translate that quality of info to a pilot, over a squalk-box intercom in 9.024 seconds.
A fighter traveling 100 mph faster then your bomber will take 2 minutes and 3 soconds to close to within 1000 yards from 4 miles out. So all you have to do is make your 9.024 sec loop through the gunner positions once every 90 seconds and your covered. And if the Buff didn't have tail gunner, or belly gunner, than you should be blind to planes attacking from that position. In such cases F3 is providing the function of crewman that never exsisted!
This "SA in a bomber that the crew would have provided" excuse is the weekest of all excuses for needing F3 in a buff.