Custom game options
I would like to see more custom game options with more tweak-able rules, including allowing all game modes & all player count limits on all maps. I can't be the only one who would enjoy an afternoon of "all-for-one URF hexakill" on Howling Abyss. Being able to enforce item, ability, and champion limitations would also help the small dedicated custom-game-mode player base. (EX: you wouldn't have go argue over which champions are perma-banned in hide and seek if the host could set banned champions) Unlike other game modes, nothing that you do to Custom games is going to interfere with the player base at large, so more options simply = better.