action=raw's original uses are largely obsoleted by the API and ResourceLoader, so I wouldn't worry too much about adding new support for other data types.

(In reply to comment #1)

action=raw's original uses are largely obsoleted by the API and ResourceLoader,
so I wouldn't worry too much about adding new support for other data types.

The thing is... i already had this implemented,. and then deliberately took it out again. But I can't recall why exactly. Security, perhaps?... Someone convinced me it was a bad idea...

The reason why action=raw is not supported is that there is no way to report the content model to the client (The HTTP header Content-Type can be used for the serialization format, but would be inappropriate for identifying the model). Legacy clients accessing pages with action=raw will expect wikitext, but may receive something else entirely, like JSON.

action=raw does not provide a good way to report all the meta data necessary for interpreting the data itself. So, it is disabled for anything that is not text.

Keep in mind that action=raw is a legacy interface and deprecated. Use the API instead, or SpecialExport. Both report the content model and serialization format along with the content.