Great, now I can try to collect my puzzled brain and recover!
I had just a funny remembrance: CMSMADESIMPLE has an addon, which uses the page-layout for non-system-pages, to integrate an online-shop. It is called something like "shopskin helper", www.cmsmadesimple.org
They do like that:
you have to set 2 defined comment-lines in the template, 1 before the contnent and the 2nd after the content before the footer
than you run a script, this copies the parts above and under content, writes top.php and bottom.php
and in the non-system-pagetempate you include those
if you run that script by cron-job, it is always uptodate
that could have been a solution for you as well, but my grey cells were to slow..