On (1): "File:Module:Foo" may not be invalid* but UploadWizard and others automatically strip the ':' in File titles, so it's not really a supported title and I count few hundreds in Commons. It would be ok to make such titles illegal and rename existing files: in fact, I see it was proposed already by John Vandenberg in https://www.mediawiki.org/wiki/Requests_for_comment/Associated_namespaces#Automatically_moving_pages_on_namespace_creation.
Nemo
(*) https://www.mediawiki.org/wiki/Help:Bad_title (and friends) would use some editing.