I think you can make it easier. I will not copy the template, I will change the presets of the same template. That's easy going with the component css2switch:
extensions.joomla.org/extensions/style-&...plating/4252/details
you must only change one code line in administrator/components/com_css2switch/css2switch.class.php at around line 51. in function leseTempVerzeichnis change prefix='temp' to prefix=''
Now you can give each menu-item a preset - without copy the template files.
Cheers.