I mainly play (sim) Be-A-Gm so :
Make the Draft less boring/predictable - Maybe have something like a scout's recommended list or something? Projections would also be cool (ex. 5th Rounder 20yr old SNP = Scout max (2nd Liner, low chance)) Another thing that could be added are scout notes for each player? (ex. Pros = Big body, can skate - Cons= poor work ethic, low hockey sense)
More late round steals! Obviously not every late pick should equal a star but a couple of them should turn out if developed properly. (In NHL 12, I drafted a DFD with the last pick and he developed into one of my best d-man. NHL 13, I think I've seen only 1 good player drafted after 2016 past the 4th round)
Potential should fluctuate - A good year brings the potential up, down year drops it. Obviously it shouldn't change too much.
Add a Versatility rating scale 1-5 (1 = Has a tough time playing 3rd line center if a 4th line winger, 5 = Can easily adapt)
Get rid of the phones - Seriously, it seems dumb having trade limits at the TDL & Draft.
Trading during draft - At least for the 1st round, you should be allowed to make trades between picks.
Being able to retire numbers - Okay, not as important but it would be nice to be able to retire numbers for your players after they retire.
Development for defencemen/goalies should have higher age cap - It takes longer for them to develop, I think the cap for goalies should be 29/30 and D-men 28/29 . Forwards can stay the same at 26/27.
Mid-Season contract extensions - like real life, if a player is in a contract year they should be available for contract talks.
Players who haven't shown anything should not be asking for lots of money.
Thats all I can think of right now, Be-A-GM has so much potential.