Make sure you move any associated css and server side code that goes with the functionality you moved into the plugin so you can keep it all together. That is the benefit of plugins over regular includes:
1) It allows you to keep your html, header, and server code all together.
2) Allows you to use relative links from sub-directories and updates them to work whenever and wherever the plugin is used.
3) Because the links can stay relative to the plugin location and not the page that uses them, all Dreamweaver functionality can be used without adjusting manually to reflect the end location.
Thanks for trying to clarify. I fear that your explanation makes me think I will be including a CSS file multiple times (in the parent template and also the plugins) OR will be cutting the CSS apart and created multiple CSS files specific to each regional plugin.?
I think a nice template (set of files) showing the benefits of this extension would really help people see any benefits if presented in a actual working environment?