Hi Ola,
I have something similar on the CMS I am working on. It does use the template on CR like the CR index.vuh file. But if it fails to find one it looks for the template of the folder (parent_id). If it still fails it will return a default template.
Here is the code, although that code is likely broken right now.
http://cvs.openacs.org/cvs/openacs-4/contrib/packages/bcds/www/templates/default.tcl?rev=1.1&content-type=text/x-cvsweb-markup
Also I think CR has some basic API to reach what cr_get_live_revision_from_url it trying to achieve. You can use content_item__get_id. Once you got the item_id just look at cr_items.live_revision. This is what I used, so mine is nothing different just a tcl api wrapper.
Hope this helps and gives some ideas.
