He's talking about using it for a 480mph speed brake because he's diving faster than he should. At those speeds the doors probably wouldn't function or would rip off (possibly damaging the plane from the 480mph shift in flight dynamics as it ripped off).
What he's asking for may very well have been catastrophic in nature, but he's just looking for a gamey loophole to fly in a way he shouldn't fly.
Krusty, what I do is to open the doors in order not to reach 480. In a mossie6, if you are already at 480 and still pointed down you are dead, no doors will save you. Currently, if I am going 300+ mph and need to dive on someone below, or make a steep dive bombing run (wing bombs), I have to ride the rudder in order not to reach 480 is a couple of seconds. The opening the bay helps a little.
The doors are already in the game and they function if I load up bombs and ditch them on the runway. This is a stupid work around and the message "your plane does not have a bomb bay" seems kind of silly and breaks the internal logic of the game: The exact same plane with the exact same current loadout operates differently depending on how it started its sortie. In other words, without any bombs on, one has to remember whether or not he had bombs sometime earlier when he plans to dive on a target. This is the reason why I think this is a bug and asked for it to be fixed.
Finally, it was done in reality. I do not know of any official speed limits to opening the bay doors. They were definitely built to be opened at 300+ mph because mosquitoes were supposed to be able to drop bombs at such speeds. The gears too were used at high speeds, though in the game I can only lower them under 190 mph. I am not asking to change the way gears operate. Unlike the bomb bay, the speed at which I can lower the gear does not depend on whether or not I had bombs when I took off.