Like Enhancing JS, it would be very interesting to import other css files from the plugin!
It could be a free text area where to write a list of external css files urls to link in the header of the pages, i.e http://fonts.googleapis.com/css?family=Ubuntu:300,500,300italic,500italic
If would avoid to use @import directly from the css code, which delay the css loadings and make all the pages longer to display! (cf. http://www.google.com/url?sa=t&rct=j&q=%40import&source=web&cd=6&cad=rja&ved=0CHUQFjAF&url=http%3A%2F%2Fwww.stevesouders.com%2Fblog%2F2009%2F04%2F09%2Fdont-use-import%2F&ei=tEQtUPGxOvTc4QSxlYDwAg&usg=AFQjCNEgks6FNn586ANOQ9zvfWaFy4Nd0g&sig2=MoqgwKeV8CLPSrvtppHSZw)