Having played several iterations of this mode now, I do prefer Summoner's Rift and really enjoy the mode in general. I do have a suggestion that I think would make the mode more interesting. My one gripe is that I get tired of playing with or against the perceived most OP champs. While there are some games where people pick "off meta" champs, for the most part, it's a rotation of nearly the same bans and nearly the same picks.
I propose a change that would force the all for one meta to frequently evolve:
Every day, add to the disabled list two champions, the most picked/banned and the highest win rate (given a certain % played threshold).
The upside is an ever shrinking champion pool will force players onto different champions as the event goes on. The downside though is it is possible if a player doesn't have an opportunity to play in the first couple days of the event he/she may miss the opportunity to play a particular champ. In my opinion, the benefit is worth the cost.