I'm not sure if the automatically embedding youtube videos is a good thing. A separate "[youtube]" tag might be a better idea, this way existing posts with inline links in paragraphs to youtube videos don't get translated to embedded videos, breaking up the paragraph.
For example:
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis a pretium libero. Donec at tortor nec purus imperdiet pulvinar. Maecenas dictum tristique felis at rhoncus. Aliquam erat volutpat. Nam laoreet nunc leo. Curabitur sem tortor,
" class="bbc_link" target="_blank" rel="noopener noreferrer"> commodo sit amet suscipit at, semper sit amet enim. Nulla volutpat sagittis ullamcorper. Vivamus a nibh at dui vestibulum suscipit. Aliquam id mauris dui. Quisque dictum gravida euismod. In nunc ante, bibendum nec vestibulum nec, iaculis id est.