[RansomOttawa]

Or...how about putting a rotating ring around it with a gun mounted on it, so you could target 360 degrees around the ship?

The Russians experimented with a circular battlship design in the 19th century. It was a complete failure; the worst aspect of the design was that off-axis recoil from the ship's guns set the whole thing spinning. I can't imagine that would be any better on a flying gunship than a floating one.

[Boogieman]

“off-axis recoil from the ship’s guns set the whole thing spinning”

Ah, that’s why the aliens use recoil-less death rays. Explains a lot!