Which CMS to use?

I need to create a web (or non-web) system where a user can create a template layout with tags and placeholders for elements. They could then add new pages to this template. My system would need to pick up any elements that have changed and create an XML of the tagged content. I was just wonderin开发者_StackOverflowg what would be the best CMS or any other software I could use to implement this?

Perch CMS (a commercial, lightweight CMS, http://www.grabaperch.com) may be a candidate system in that it can allow a user to use one or more templates with tags/placeholder elements to create or update pages.

However, the templates need to be created by the site developer. The user editing pages cannot actually create the templates.

Perch CMS uses a MySQL database to save the element content, so the XML file of the tagged content is not readily available.

Perch CMS does have a good API so you could export the element content into a file if needed.

Most other systems like Cushy CMS tend to save the edited elements in the original page, not exactly what you are looking for.