Replace TinyMCE with Custom Built Editor

You can do that with js/jquery if you want :

$('#postdivrich').hide().after(your custom editor div);

You can add inputs with jquery and save them with :

add_action('save_post', 'save_the_post');
function save_the_post(){
        global $post;
        update_post_meta($post->ID, 'field_name', $_POST['field_name']);
}

Or use a metabox and replace standard editor with it (width jquery).

Hope this help someone 🙂