When working on a site, you should be able to set things as an include so it can copy immediately to another page, thus keeping the structure. With php, I normally do something like
<?php
include('folder/header.php');
?>
And this would include the header for the page structure. In BSS, you should be able to make a file and include it to the page...
Also, how about letting us export as other page extensions like .php ?