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.