TYPO3 Core

its not that much...
here we go: typo3/sysext/cms/tslib/class.tslib_pagegen.php
update the following:

in Line 628 (renderContentWithHeader) change:
$GLOBALS['TSFE']->content.=TSpagegen::inline2TempFile($style, 'css', $GLOBALS['TSFE']->config['config']['inlineStyle2TempFile.']['media']);

And update the following method:

/** * Writes string to a temporary file named after the md5-hash of the string * * @param string CSS styles / JavaScript to write to file. * @param string Extension: "css" or "js" * @param string Media (for CSS): String like "screen, presentation", "all" or "print" * @return string <script> or <link> tag for the file.
*/
function inline2TempFile($str,$ext,$media=null) {

// Create filename / tags:
        $script = '';
        switch($ext)    {
            case 'js':
                $script = 'typo3temp/javascript_'.substr(md5($str),0,10).'.js';
                $output = '
    <script type="text/javascript" src="'.htmlspecialchars($GLOBALS['TSFE']->absRefPrefix.$script).'"></script>';
            break;
            case 'css':
                $script = 'typo3temp/stylesheet_'.substr(md5($str),0,10).'.css';
                $mediaTag = ($media === null)'':' media="'.$media.'"';
                $output = '
    <link rel="stylesheet" type="text/css" href="'.htmlspecialchars($GLOBALS['TSFE']->absRefPrefix.$script).'"'.$mediaTag.' />';
            break;
        }

// Write file:
        if ($script)    {
            if (!@is_file(PATH_site.$script))    {
                t3lib_div::writeFile(PATH_site.$script,$str);
            }
        }

return $output;
    }

i.e this would be nicer as a stdWrap

It is not possible to have subproperties inside "config". I.e. it can be only config.whatever but not config.whatever.whateverelse.

strange - i thought ive seen it for some extensions (config.coolExtension.bleh) - but indeed - might be an unclean solution.

however, than call it
"config.inlineStyle2TempFileMedia"