Question: just 1 click ..and it duplicates ALL content, settings, css, plugins..

im looking for a plugin that adds a new link to Sites admin; 

Edit | Dashboard | Deactivate | Archive | Spam | Delete | Visit | **DUPLICATE**... 

it should copy ALL settings/configs. 
and create a new subdomain instance in the **existing** Multisite

Answer: 
A quick edit option for |Delete|Visit|DUPLICATE seems a bit too tailor made.

Nonetheless, this plugin does exactly what you want with 2 clicks (on its own screen).
<http://wordpress.org/extend/plugins/add-cloned-sites-for-wpmu-batch/>
There are a number of plugins that backup the database as well as WordPress files.

Looking at the [plugins associated with the backup tag](http://wordpress.org/extend/plugins/tags/backup), the following look useful:

* BackupWordPress
* XCloner
* Backup and Move Plugin