No more auto-fill
I don't play the game too often half because it's too addicting and half because I'm tired of it, but when I do open League of Legends I hope to play a game in the lane I want with the champion I want. The last thing I want is to wait in a long queue just to get a role I didn't apply for and end up waiting 45 minutes additionally for the game to end. And I don't ask for everything to be perfect, I am ok with a lengthy queue as long as I get to play exactly what I want.
Another big problem that auto-fill creates is that everyone dodges queue because they got auto-filled. I have literally waited 40 minute queues to get into a single game only to get disappointed with an auto-fill role. I really didn't want to play support after waiting for so long so I tried out Yasuo support, pissing off everyone else too.
Some might say "Play Blind Pick then". No thanks, I would rather not join a game where I'm going to be left with support anyway and then get annoyed by immature teammates that really just join Blind Pick just so they can flame others.
All I want is the Team Builder mode there was about a year ago, where I could just wait as long as I needed to but in the end I would get the game I wanted. Or maybe you could add some fun supports that aren't tanks and are still competent :)