Did you all know that the original CMS package contained the site-map mounting funtionality?
We do want to build a nicer user interface over site-map, i think Lars is working on this with the acs-subsite admin pages rewrite.
I was looking at it from the other way around, in that the CMS could add pages to any site-node, and eventually would be able to supply replacement adp templates for any adp in the system. This seems liek a better way to integrate with existing OpenACS functionality.