On the whole I'm kind of allergic to inventing an entire new concept
that has as much overlap with extensions as modules seem to. I'd
rather try to understand what functional requirements we're missing
and see if we can add them to extensions. Yeah, we won't end up being
bug-compatible with Oracle's feature, but that's not a project goal
anyway --- and where we have tried to emulate Oracle closely, it's
often not worked out well (poster child: to_date).
Developers need a way to group related objects in some fashion so
that they can be more easily reasoned about. Modules are just the
way to do this in the spec, but if we want to leverage extensions,
that will work too. Many users who need this only have access through
a database connection. They wouldn't have access to the file system
to add a control file nor a script to add the objects. Enhancing
CREATE EXTENSION to be able to create some sort of empty extension
and then having the ability to add and remove objects from that
extension may be the minimum amount of functionality we would need
to give users the ability to group their objects.