I wonder if the Molins loader could have been designed annular, so it could wrap around the breach instead of piling it all up on top like that.
It's likely a lot easier. I'm pretty sure the Mollins loader was designed to fit the aircraft, i.e. the pilot, fuselage size and CofG considerations needed to put the system into an existing aircraft.
The A-10 went the other way and essentially built the aircraft around the gun.
Designing a podded gun and feed system to be an optimum pod is very likely (bound, to be, really) easier than fitting it into a pre-existing aircraft.
Paul