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.
