I got tired of changing my plugins CSS everytime I update them (you know, searching the backup because you forgot that it will be overwritten, etc.), so I thought about the following change in the CSS dispatcher:
* changing the order of CSS loads:
* default CSS
* plugin CSS
* template CSS
This way you could include CSS for the plugins in the template which would overrule the original ones. You would just have to add it to the style.ini.
I made some changes in my wiki installation and it works, thou, I´m not sure about some side effects yet.
detailed description can be found here: http://tag-am-meer.info/wiki/dokuwiki:snippets:plugin_css