At the time I'm writing this it's late and I could go on for hours about what I want to see. So here's a quick list:
Better game pace
Quicker response from the balance team on gamebreaking issues. Like what they did to funnel, but a bit faster
A goal to achieve after reaching gold
For Riot to keep an overall rank. I'd much more willing to give positional match making a fair shot if I got to keep my overall rank.
Another AP item rework. The one we got flopped bad
More ways for immobile champions to deal with mobility
Meta's that are less defined, I think that's the right term
Hide and Seek as an experimental mode (literally just to make sure everything feels good), before it becomes a featured mode
A better system for featured game modes. The first system overexposed too many, and now they're never around
More reverts/ partial reverts to failed class update champions
are the big ones
Duskblade removal
A complete revamp of the Sorcery Tree.
Changes to common pro champions to keep them out of the
group
New Champion/VGU podcasts to come back
Skins for less popular champions
Nexus Blitz is a success.
And as an overall goal, I want to be able to spend a whole day playing League and go to bed feeling like I just had an awesome day. It's been a while since I had that, and I might actually cry tears of joy if it happens again. I think that gameplay wise (massive emphasis on the word gameplay) Riot is slowly moving back in the right direction, and for once I'm looking forward to preseason.
Also, have you seen the tower barricades coming in preseason yet? I think that idea has some real potential.