Content Type of a Document

There's currently no way to do this as far as I know - it would require a relatively complex parser (especially considering that not even all document types have a consistent content type indicator). It might be a good use case for a plug-in though.

As far as I know, I don't believe that there is currently any way to do that either

Right now I don't see any plugin created in shared components, Though some extension we can change to compatible ones and this requires general user knowledge like what are the compatible extension e.g. docx to doc or etc. But there might be cases like changed extensions will not work.

If you want to create a plugin then you may need to do research for compatible extensions so that after changing of file you will not end up with displaying all greek.