Ibis door guns cant fire at targets that are bellow and a little bit back (because of pylons) but without them guns still cant fire at targets in that huge blind spot.
So, why wont try and make their firing angle be variable, that will depend if you have your pylons equipped or not.
Also, its quite weird that door guns cant rotate to the back, instead of 180 degree of firing angle you have ~130 with sometimes is pretty bad, especially when you flying above some ground targets.