Champion sets

This has been an idea I've been mulling over for about a week, but why not add a feature to the game much like item sets, for champions? That way you can separate your tops from your mids, your ideal junglers from your crap junglers, or even the champs you just generally play a lot from everything else? When you start to get about halfway through the champion pool, you begin to have issues finding champs sometimes, which can often cost you valuable time tweaking your masteries or something pre-game.