Add the 'hybrid_media_grabber_args' and 'hybrid_media_grabber_media' hooks.
apply_filters(), not add_filter().
Use $this->type instead of hardcoding 'audio' and 'video'.
Need space at the end of the 'browse' argument.
No need to remove shortcodes when 'the_content' is called.  It's just extra stuff being processed and isn't required by the WP theme review.