Ability to override included files in child themes

I was trying to look after a way to override included files into the main template folder from a child theme. I found this post on worpdress forums, and it would be great that this theme can include this. Maybe is a huge job to change almost all the theme, but it will give a huge opportunity to change the skin in case we need or add new features to the theme.

I quote it here:

One of the biggest limitations of child themes right now is that only the child theme’s template files are automatically loaded. If you want to override a file that the parent theme includes (e.g., themedir/lib/foo.php) then you have to find the file that calls require_once(TEMPLATEPATH . ‘/lib/foo.php) and override it to call require_once(STYLESHEETPATH . ‘/lib/foo.php), and in some cases you have to do that 3 or 4 times until you get to the top of the hierarchy.

It’d be better if there were some kind of wp_require_once() function that would take a path (relative to the theme dir), and then check if there was a child theme file to replace the parent theme one.

function wp_require_once($path)
{
if( TEMPLATEPATH != STYLESHEETPATH && is_file(STYLESHEETPATH . $path) )
require_once (STYLESHEETPATH . $path);
else
require_once (TEMPLATEPATH . $path);
}

Then theme developers could use wp_require_once(‘lib/foo.php’) instead of require_once(TEMPLATEPATH . ‘lib/foo.php’). If a child theme was being used and had a replacement file, WP would load it; otherwise it would load the parent file.