Its not that easy because of all the places that the wrapper would need to be used. You don't know how fullscreen.php will effect the modules section of this site...or the themes section...or any of the admin scripts that run. This is a large site written from scratch that can't have things plopped in here or there.

Also...you will notice that there is only one php file for this site...index.php...and it will stay that way. So again...this change will effect more than you could/would/will ever know.