CSS stylesheets

Great product but 5 stylesheets are a bit limiting. Can I make a simple suggestion that will allow everyone to add there own stylesheets without any major changes to the scripts. If you add this option as you have done with the header & footer into the html head after the current CSS <link>:
{include_if_exists linkfile="include/site.css"}
I know that the method above is for including files but could be modified to look for CSS files and add the following link after the current style sheet:
<link REL="stylesheet" href="include/site.css" type="text/css">"}
It needs to be after the current stylesheet so that styles can be modified without touching the original stylesheet. Problem solved and anyone can then apply any changes to the site.css without changing the original stylesheets and therefore make each site they create unique.