OK I like the motive behind the OP, but I have a different way to get there.
For actual firearms, you have to "Zero in" your sights or optics. You do this so that the recital or aim point will be where the bullet hits. This is usually done at a certain range.
It would be neat if while we were in outfitting we could adjust the "zero" on the targeting CPU to a certain range. Then the fixed weapon mounts could be angled accordingly (within reason).
For example, if using frags, you can adjust the recital to be zeroed in at 1.5-2 km, and angle in the fixed mounts permanently by 5 degrees.
This way you can keep viability of gimbal, and add some increased customization when using fixed.