Are Nebula pods interchangeable mission packages?

Can Nebula-class ships interchange their mission pods?

The participants disagree: one reading treats the pods as modular mission equipment, while another treats the configurations as fixed subclasses.

The Nebula's different pods invite comparison with interchangeable StanFlex mission equipment. A competing interpretation treats the visible configurations as distinct subclasses with fixed roles. The participants disagree over what the fictional evidence establishes about swapping the pods. The comparison remains useful for distinguishing a family of related designs from a ship that can actually change mission equipment.