More Permanent Game Modes

I love paying classic on Summoners Rift, but I don't always have time to play for the full hour it takes (usually) to queue up and play.

We need some more permanent game modes that let you choose which champion to play (unlike ARAM), has fun/twisted rules, and takes like 15-30 minutes for a game. Hexakill was great, URF was amazing, even doom bots was pretty dang fun. Why don't these game modes have a more permanent place in the League of Legends repertoire? It just feels like we need a bit more variety as far as game modes go.