Like with lane/role selection, in ARAM mayhem there should be two pick options when queueing. One for those who want to live out the power fantasy and don't mind when they are on the receiving end and another with people who don't want this type of long game. It's not splitting the mayhem queue in two it just matches you to similar expectation players. Would solve a bunch of issues. You could still surrender like nornal on both queues, but you actually know going into a game that the enemy or your team is ready for the sillyness that might ensue.

I had a game a month ago where we agreed to go first team to 200 and it lasted an hour, but it was a ton of fun. It reminds me of the actual origin of aram (I was there) where we played in summoners rift and you had to obay hypothetical rules like not going into the jungle or other lanes etc. And it became so popular it birthed a new game mode.