Answering My own question..
That was easier than I though.. I used the post_link
filter to modify the permalink in the following way..
function custom_permalink( $permalink, $post ) {
// Get the categories for the post
$post = get_post( $post_id );
$category = get_the_category( $post_id );
$post_year = mysql2date("Y", $post->post_date);
$target_cat = 6; // Category we'd like to change permalink for
if ( empty( $post_year ) ) return $permalink;
if ( $category[0]->cat_ID == $target_cat ) {
$permalink = trailingslashit( home_url( $category[0]->slug . "https://wordpress.stackexchange.com/" .$post_year ."https://wordpress.stackexchange.com/" . $post->post_name . "https://wordpress.stackexchange.com/" ) );
}
return $permalink;
}
add_filter( 'post_link', 'custom_permalink', 10, 2 );
And of course, flushing permalinks by visiting the settings > permalinks page.