Drop-in Drop-out gamemode

Wouldn't it be fun to have a game mode where players were given x amount of time, say 5 minutes, in a game before being switched to a different game?

Say you queue up with 4 friends, and you start a game. at the 5 minute mark you'll be sent to a different game entirely and replace the previous summoners so that you will take over their champions. So on and so forth until you either win or lose one. It would be a fun (though frustrating) way to have players try new champions, and teams to either be thrown in a position where you could be fed or could be feeding.

Or you could have it so that the players always keep their champions in matches, so that when you switch, you don't have to worry about being in a bad position or underfed.

I just think it'd be interesting to see how players and statistics would change...of course it'd be a temporary game mode, but it would be fun for a while.