Honestly, if I'm losing, I want the other team to tryhard. I want them to just get the kills they need get the baron end the game and let me move on (of course -I'm- going to tryhard to get that turnaround fight or mythical jinx-rocket-baron-steal... got a dragon before but never a baron.)
What I -don't- want is for them to screw around ignoring objectives while farming up and making the occasional pick before they finally actually finish a game that had a nearly inevitable conclusion 30 minutes earlier. I also don't want -my- team to do that because that 'nearly inevitable' becomes less and less inevitable as everyone scales up to level 18 and max build where the idea of a 'lead' finally becomes meaningless. That's one way to throw a game, and one that is particularly painful to both the winning team (who thought they had no chance for the last half hour and suffered through it all) and to the winning team (who thought they couldn't lose for the last half hour and are feeling pretty stupid right as the defeat spash comes up).
Since you specifically mention Zed I want to point out that the 30/0/2 Zed that bitched about KS when he got those two assists is -not- trying to win, he's just padding his score, and that's a small part of what I mean by 'screwing around and ignoring objectives'. (He's also probably the -only- one in the game having fun, since the rest of his team probably wants to get the objectives and win and the enemy team just wants to stop being killed by zed. Replace 'Zed' with Kassadin or Riven or any snowbally dueling champ, as applicable for your games, of course. Zed is just flavor of the month.)
On the merits of your idea, it just doesn't make sense. There's already unranked queues that are considerably more casual than ranked. As long as there are victory and defeat banners, people will be trying to win. Nobody's going to join a game with a winner and a loser intending to lose and it doesn't make sense to report people for trying to win a game... that's the objective of the game!
I'm not opposed to a more casual queue in principle, but you need some solid mechanic to make it more casual. For example, although this probably wouldn't work for reasons, you might think about not giving the players ban choices but just auto-banning the top 5 winrate and top 5 pickrate ranked soloq champions from casual queue. That'd be one way to remove the OP and flavor-of-the-month from the game and give people a little more room to experiment.
