I dont think it would be a bad addition if rear gunners on planes such as the IL2, 110, SBD, TBM, etc... be made to auto fire like the ack on airbases.  Not as accurate as a human controlled gunner could fire, but atleast something that has a chance of hitting if the bogey hangs around long enough.
There is really no purpose to gun for someone score wise, and its not really feasable to ask for a gunner every time you take off.  Human manpower is limited.  I dont believe you should need 2 human players to take full use of an airplane.  Strategic level bombers I can understand having to gun yourself...but single or dual engined attack planes I think should have this option.