Get rid of the GM Rep ****. There's no reason to get punished for turning down terrible deals.
Goalie fatigue for GM Mode. It would add a bit of extra realism to the sim.
Something needs to be done about the potential system. I miss how they separated the potential into 3 categories so it was easy to tell if a player was going to get better offensively, defensively, or both. I hope they bring the old system back.
Trading AI. I know they tried to improve it with NHL 13, but it didn't really work. I like that they added the portion to show who they are willing to get rid of, and who they want from your team. That was actually a very good addition, but they still need to think more like NHL Gms. It's so annoying when a team just drops all their core players because they are riddled by injuries. It just doesn't make sense.
Waiver issues, I don't think I need to explain that.
Draft definitely needs work. There needs to be more busts and steals. There's no sense in even using your draft picks for the 3rd-7th round because they will never become NHL players. I want that fixed.
It would be interesting if you could pick a specialty for your scouts. Their specialty area would make them more likely to find steals in that particular area of the world. I think that would add some more fun to the draft.