Simply put, when you complete a set for a certain job, have a book that logs this and allows you to go back to that complete set any time you like.

So, for example, if you have the Templar Set (Which there is a feat for), you can save it in your Glamour book, and go back to that set any time you like without having to stockpile the gear to do so.

This is really just a simplistic version of the DCUO Styles settings, which I'd pay heavily to introduce to this game :P.