I think actual physics for the goalies would be a huge change.
A lot of goals in the NHL get scored when you get the goalie out of position. The way goalies move and react now they get back and forth like they're on pavement. There's no sliding when they move. A goalie can easily rocket to one side of the crease, and then back without fear of sliding out of position. A goalie making an aggressive save to one side is never open to a wrap around attempt (Not just because they're nearly impossible to pull of as a skater) but because they can just slide back around before anyone gets to the open net. There's no realism in their movements, because it's all animations without real physics. Watch the diving save animations. The goalie doesn't really "push off" he just kind of jumps in place and sprawls through the air.
Now, imagine instead the goalie has to actually push off, and he actually slides laterally across the ice. He has inertia, so you're on the powerplay. He follows the puck from the left circle to the right, and the defense breaks down in the middle, leaving an open gap to quickly pass it back. You launch the puck back, and the goalie is still sliding with the first pass. He plants and starts to push back, but he's still sliding a bit and doesn't get over in time and you narrowly put the puck between the post and his blocker.
Another thing would be positioning. So many goals i've scored have come from the fact that the goalie deflected an easy wrist shot on the ice off of his pads and into the net because instead of coming out and covering the bottom of the net and the sides, the often just sit inside the blue paint and pivot in place, which leads to a puck that would have been bounced into the corner going into the side of the net.
That would be huge. Goalies like Smith, Allen, Brodeur, who all like to come out and move the puck themselves lose a huge part of their value because goalies are basically nothing more than a danger outside of the crease.
Same for the powerplay. Goalies usually help on the clear, stopping the puck behind the net, and skating out into open ice on line changes to launch it back up the ice and take advantage of the change, but in game they just sit in net forcing you to wear your guys out going end-to-end each time the puck gets cleared.