OK, best approach for me is a hook:

Could please someone commit to trunk:

./program/include/main.inc.php#line1374

/**
* Output HTML editor scripts
*
* @param string Editor mode
*/
function rcube_html_editor($mode='')
{
global $RCMAIL, $OUTPUT, $CONFIG;

$lang = $tinylang = strtolower(substr($_SESSION['language'], 0, 2));
if (!file_exists(INSTALL_PATH . 'program/js/tiny_mce/langs/'.$tinylang.'.js'))
    $tinylang = 'en';

$hook = $RCMAIL->plugins->exec_hook('hmtl_editor', array('abort' => false, 'mode' => $mode, 'tinylang' => $tinylang));

if($hook['abort'])
    return;

$OUTPUT->include_script('tiny_mce/tiny_mce.js');
$OUTPUT->include_script('editor.js');
$OUTPUT->add_script('rcmail_editor_init("$__skin_path", "'.JQ($tinylang).'", '.intval($CONFIG['enable_spellcheck']).', "'.$mode.'");');
}

___________

Regards,

Roland