I was unaware that the arrow keys could be used to aim guns as well; that does help a lot for slower-turning guns, and allowing WASD to aim as well seems like a no-brainer.
Limiting the scope of 'free-looking' to the maximum turn radius of a gun is another option that could help discourage 'gun-squatting,' and I think implementing some to way keep guns from resetting to their neutral position after getting off would help a lot.