I'm big on EASHL so most of my fixes are about that, everyone add whatever you want, and what you think of mine. 
 
All around gameplay: Bring back the NHL 09 passing but make it easier to intercept passes. Make it so the goalie reacts differently each time there's a rush (ends glitching). Make it easier to score opposite corner (after NHL 09 they tried to take out the curve shot, and kinda killed the shooting) Make faceoffs less clean (it's so unrealistic). Make it so that user goalies can't just sit on the goal line and save everything. Add team brawls (but make them rare). Make it so the goalie actually gets knocked around. Make deflections take more skill, and occur more often. 
 
EASHL/OTP: I'd love to see a team practice mode added to club. Also make it so clubs can create their own jerseys. Make it so there's a "vote to skip" system during replays and intermissions. Make it so there's more customization on your player (there's only like 4 white guy faces, it's really dumb). Make it so the player equipment matches the team uniforms. Add a playoff system and different divisions (10,000 teams all competing against each other is pretty dumb, it was way better in NHL 09).  
 
Well there's definitely a lot I forgot so I'll add it in comments. Be sure to add what you guys think. 

Addition: Make it so the menus stop freezing my fucking xbox.

Headshots. Let's make things more realistic and add headshots that cause player injuries. Depending on your salary, and league status, you can get away with hitting people from behind into the boards at top speed and pretty much avoid any major suspension, or you can be a goon that gets suspended indefinitely every time you take out a star player. How many concussions did we have in the NHL last year to marquee players? Let's at least reflect that kind of thing in the game--call it the Scott Stevens mechanic.

see my review of 10 :>

Addition: add intentional offsides, for some reason they're not in NHL 10. 

Take out the fucking momentum. So many times as my team just thrown in the towel and become slow as hell in the 3rd. When in the first i was skating circles around my friend. All because he scored 2 quick ones at the end of the second. The second goal being a clear break away as his guy hits the nos button. Also tone up the hitting just abit more. Frustrating when i'm pronger hitting gomez and he bounces right off me.

What about having the 1980 USA team,goalie fights,goalie injurys' like mlb the show being able to record chants

I would like to see better goalie AI.  I feel it actually got worse in 10 from 09.  It seemed almost impossible to beat the goalie with a high wrist shot.  They also had the worst rebound control possible, the goalie could not hang on to the slowest moving low shot to save his life and they always kicked the puck away to the worst spot.  Now I know its difficult to make the perfect goalie but I definitely see that as a big opportunity in 11. 
Additionally, I would love to see them rework the feel and controls of defenseman in the EASHL.   I like to play as the defense because I get bored playing forward, but your so handicapped.   Just clearing someone out from in front the the net is way more difficult than it should be and one-time passes often go right through you even if your in good position.  Those are a few of the changes I would like to see, maybe the new physics engine will help on some of these.

Less crazy dekes and the ability to upload highlights straight to YouTube/watch within the game, otherwise it's pretty much perfect.

Less Hockey.

They dont need to improve the goalie AI so much as they need to give the goalie more animations